Keep in mind that the weather conditions around when you spread fresh (or not well-composted) manure, and whether horses are on or off the field, is going to have a big impact on the re-infection risks.
It does help if you spread it thinly, and when it’s hot and dry - those eggs will die in a hurry.
If it’s cooler and wetter, those eggs can hang around a long time, and hatch into infective larva when temps are warm enough
Spreading during wetter period of with temps in the 45-85* range is great for egg survival and hatching. If the horses aren’t on the field, those hatched larva will quickly die without a host.
Spreading below 45* means eggs will be hanging around until it warms up.
Spreading above 85* and dry, means eggs will quickly die (days, not hours).
They’re just things to think about . I regularly drag my field (it’s too large to pick up after 3-4 horses), and in the Winter, so technically it’s all the worst time. But it is what it is, and my FECs are regularly clean/low. Dung beetles do an excellent job from Spring to late Summer, piles disappear in a matter of days sometimes. For that reason I avoid ivermectin in the Spring deworming, and use moxidectin (Quest Plus)