M friend has had a hot tub for over a decade and it’s always cranked to 104, which is the highest you set it without setting off the regulated Turn off Switch. Has 4 kids and the couple was using birth control most of the decade. It’s just an example and so many variables come into play. I did a quick internet search and found this study by McGill University and talk about Heat and Hot tubs and how they affect male fertility. It’s a good read and I learned quite a bit. Apparently hut tubs and excessive heat to the testes can cause issues for weeks but it does show that it reversible, which is good news.
We didn’t have particular struggles, but it gets less fun quick! Less oral foreplay, sex in carefully timed clusters when you’re not remotely turned on, special lube, rising stress monthly, supplements, a miscarriage or two (you wouldn’t notice if you weren’t trying, but you are, so you get hopes-raising positive tests, then a letdown), a grim wondering about medical intervention, a sperm analysis (jerking off and presenting your handiwork to tech is a bit odd), etc.