I wish someone had told me this: once you put muscle on your frame it tends to stick around.
If you bulk up and turn into Hercules over the course of a few years you can scale back your training volume dramatically and as long as you keep your diet right, you will continue to be a jacked and cut dude for many many years.
I'm sure this gets less true as you age but it seems to apply to me in my 40s.
Maintenance is just way easier than the initial buildup.
I discovered this pretty much on accident when I scaled back the volume and intensity of my own training and noticed... Huh would you look at that... Very little changed.
Like on some level, it would be harder to return to the state of roly poly schlub that I was once in, than to continue being the fairly fit person I am now. I just autopilot twice a week to the gym after work, zone out and listen to podcasts for an hour while doing some pretty moderate intensity lifts, and the body stays in pretty decent shape. I barely break a sweat now compared to the first year or two.
Yeah, I'm pretty sure that Shannon Sharpe was doing a lot more than one hour per day of training when he was playing competitively. It's my observation that two workouts or practices per day is typical for collegiate athletics, even in the sports and at the schools that don't bring in money.
But after that? Yeah, no doubt that one can maintain most of that fitness with a small fraction of the time and effort.
As I said up-thread, I started running as an Army cadet, and I've continued to take annual fitness tests throughout my career. The fastest guys on those tests are guys who (unsurprisingly) were serious runners or soccer players in high school / college but who (surprisingly) did very little running after that. They could jump into the test cold and laugh their way to two miles in 12:00 (11:00 if they were really trying). I, on the other hand, basically didn't start running until I joined the Army, and I had to put in a lot of miles to break 13:00. For several years after that, though, I was able to reduce my mileage too and still run circles around a lot of people.