Hey there Gypsy!!
So we started TTC this past October and that same month we bought a house that had a hot tub so of course we were going in all the time. After a few months of no luck TTC, I read up on hot tubs and found that hot tubs definitely can cause issues with sperm. There is no real hard and fast rule about how often or how long can cause damage, but there definitely is evidence to show that regular exposure to hot tubs can impact sperm because they can't survive in high temperatures.
My husband stopped going in our hot tub about 3 months ago because I read that it can take 3 months for sperm to regenerate and mature enough for fertilization to occur. So in a way we are considering this to be our first real month trying since its the first month we haven't been going in the hot tub.
But if he is getting tested for sperm count and its coming back normal then I would imagine you don't have anything to worry about. We have not gotten my husband tested for sperm count or anything.