Those of you who have not seen one of my "Books" - get prepared, LOL
I believe you do what is working for you now and if you decide to make changes later, that you do so then.
I also believe you need to follow the protocols your county/state and your vet follows - they may require different things than our state does.
I've never personally like the combo vaccines - especially the ones that combine what we nicknamed the Mosquito vax(Eastern, Western, Venezuelan encephalitis; West Nile) with the Cold vax (Rhino 1 & 4/Flu - how many different strains can you get in one vaccine??). They all have different levels of antibodies that they build up to and the timelines can be different. I also feel that it COULD be too much for their systems - if they are building antibodies for too many things - how do they get to large enough levels to be protected? There were studies available on that once upon a time, I am not sure where they are these days OR if they've done any new ones in the past 10 years.
I have been led to believe, by many different vets, that the Flu/Rhino vaccines are only good for 90 days. If that's the case - to be fully protected - your horse would need to have that vaccine 4x/year; better a little closer and 5x/yr. Yet it doesn't prevent the horse from getting sick - just lessons the severity of the issue if he contracts it. Also, unless they've come up with something new in the last 2 years since we moved into our new property, the Rhino/Flu does not protect against that "rogue" Rhino virus that caused neurological issues at some shows in 2013/2014/2015.
Human Flu vaccines make me deathly ill - the last two that I had put me in the hospital, on fluids for 2-4 days each... Not sure what we'll do when I get even older and my immune system is compromised by my age, LOL.
In our personal experiences, since there have been some major "improvements" in vaccines (adjuvants added, different carriers for the actual protection) - we have had more and more reactions. This has been most noticeable in the Rabies vaccine but have had reactions to the Flu/Rhino as well (like the ones who've received them ALL come down sick!! and then have to be treated for upper respiratory issues) and many more fever reactions, that we didn't have from the mid 90's to the mid-2000's, to the E/W/Tetanus that we currently give.
I know that when the vet gave 15 ponies Rabies vaccinations in October 2014, 11 of them had reactions with 5 being so severe that they had to be bucketed different size water buckets, fed hay/feed at specific levels for each pony as they literally couldn't move/shift their heads/necks - some had to be on fluids with difficulty swallowing, some were on antibiotics. All 11 were on pain killer(s) and had their necks/chests hot packed for 10+ days - the 6 that could move shuffled around like zombies w/ their heads/necks level with their withers. It was god-awful!!! Larry and I were both working full time then - I had 3 adult age daughters, 1 SIL, 2 neighbors and 2 other horsey friends "split shifts" with Larry and I to water, feed, clean behind (they weren't stalled) and hot pack the necks/chests of the affected ponies. The pictures, in heavy winter coats, don't really show the swelling(s) or the abscess(s) that developed. Of course, it didn't help - we were running so hard busy the first 4 days - didn't really get any pics. By the time I took them - they were all well on the mend and they all mended. Thankfully, the weather held and cooled off w/o any major storms. The vaccines were actually from three separate lots but all from the same company. Though I didn't get any "support" re: the vaccines themselves - the antibiotics were covered (I think by the vaccine company??)& pain meds. We covered vet farm visits, fluids. Then, and my vet reminds me every time we schedule a vax update, she switched companies that made the Rabies vaccines. We also now give the Rabies only in the largest butt muscle - not in the neck or chest.
In the past, when our (full size) horses got the Strangles vaccine - from then on they always tested positive for strangles (Flashi,Oly & Wizard were on the show trail in 2012 & 2013. I know that Wizard got Strangles vaccine with his trainers in IL, don't know about the other two while in TX. Haven't had them titered to see if they would test positive for that now). Does that also mean that they carried/could pass it on? The ones who got the vaccine and the ones who didn't, never came down sick.
Here in NC, I know of farms that "carry" the Rhino that causes mares to abort. It appears to be in the soil... That was NOT fun on the ride alongs I did to a couple farms - 2 yrs in a row (SHUDDER-SHUDDER). Vet & techs/assistants wore almost full Haz-Mat suits, ICK. Vehicles drove thru "dip zones" - with disinfectant in them & were sprayed with disinfectant when we left. Other farms seemed to have issues with the Rota-Virus. Their broodmares and foals were given the vaccines for that. Again, NOT FUN at all! Those vaccines did help - as long as they weren't missed....
I have seen Pneumabort-K work, have had it work, then when our vet suggested going to the 1st dose at 3 months after last breeding date (given 3,5,7 & 9th months of pregnancy), I feel like our mares suddenly ended up "empty" between the 5th & 7th months of pregnancy - usually right before/right after the 7th month dose. It's hard to say. Again, right now, I'm not giving it at all (& Valley Vet's recommendation is at the 5th, 7th & 9th months again)... I do a booster of the "mosquito shot" and tetanus about 6-8 weeks before the foal is due- if I don't know actual breeding dates, hopefully the mare has "read the book" and we give the vax when they start developing an udder. That seems to work well. The foal is passively protected thru the colostrum and then gets their first vaccines at 5/6 months of age with a booster 8 weeks later. Not all of our foals have been tested recently - but the ones that have - have had great numbers on their IgG tests (>800) - so we must be doing something right.
I miss being able to pick and choose which vaccines I could give. I DO booster ours if we know we are going to have a heavy hurricane season &/or large mosquito concentrations. At our other place, we had large bursts of mosquitos! Here - not so much. Used to be able to get a 2 type vaccine (just e/w encephalitis) w/o tetanus (haven't been able to find it in the last few years). So, I'd give the 1st spring vax with Tet, the summer/fall vax with just the e/w - no tetanus. Can't do that anymore - you can't get the "mosquito shot" w/o the tetanus in it. Currently, we have gone back to not giving West Nile. Our youngsters get the rabies vaccine at the same time as they get their first coggins. Our ponies now older than 15 yrs - no longer get Rabies vaccine at all. Even younger if I raised them and I know they've had 5 consecutive years of Rabies vaccine... I don't give flu/rhino or Pneumabort-K anymore. This has worked for us.
There are other vaccines here in NC (Potomac Horse Fever - also passed by mosquitos; EPM - there's been a lot of controversy about this vaccine the last few years ; Botulism; Rota-virus and Strangles - may be more than this) and if our property was a problem with any of these OR we were actively showing or bringing in training ponies or for breeding, we'd do more vaccines again - based on what the local vet/our new county says to use.
I am not an advocate of no vaccines whatsoever.
I am very much into following the advice of your vet BUT being able to give your vaccines as you see fit.
AND if what you are doing IS working for your horses and you, (ain't broke, don't fix it) then don't change! If you are concerned as your horse gets older - find out more about what you are giving him - how his body/metabolism/immune system works with it - and go from there.