Sometimes the mare needs to switch pastures with the stallion, to throw her into a cycle.
Ive tried this before with heat sucess, within a few days of pasture switch.
This way she can smell his smells and visa versa.
Also a mare may not be in a full swing ovulating heat,durring a cycle,- so the timing may be off for a breeding.
I agree, wait it out til they "both" act intrested, and then breed them no more than once a day.. Usually they prefer the cool of the morning, or later in the evening or sunset.
You can tell if they are intrested if you bring the mare to the fenceline, to meet the stud, and let the stud snort/ or talk through the fenceline "nose to nose" with her.
"If she is ready", she will usually squat and pee for him..
If she is not intrested, then she will pinn her ears, or just act bored, or annoyed.