They stay around long past their peaks. Let's start from when they turn pro...
We'll go with 90s and 2000s guys There are some interesting outliers for different reasons. Their peaks are debatable but I think I'm close. Results may be very different is you start when they actually start competing in general. Interesting things you can pull from this data. I'd say to generalize that once you put your foot on the gas (meaning food, training and sups) seriously you have 10 years before you reach your peak and from there it's down hill. From the time you're a pro even shorter. Lee Priest was a really interesting one. I personally believe his dosages no one believed which would make sense why he lasted so long.
8 - 9 years. Ronnie turned pro 1990 peak 98-99
5 or 13 years Jay turned pro in 96 peak was 01 some say 09
7 or 9 years Shawn Ray turned pro 87 peak was 94 or 06
6 or 7 years Kevin Levrone turned pro in 91 peak was 97 or 99
10 years Dexter Jackson turned pro in 98 peaked in 08
6 or 7 years Phil Heath turned pro in 05, peaked in 11 or 12
5 years Dorian turned pro in 88 peaked in 93
9 years Lee Haney turned pro in 82 peaked in 91 (last show and also not a 90s guy)
6 years Chris Cormier turned pro in 93 peaked in 99
4 years Vince Taylor turned pro in 88 peaked in 92 or 93 (started later in life)
7 years Paul Dillett turned pro in 92 peaked in 99
1 or 5 years Flex Wheeler turned pro in 92, peaked in 93 or 98
17 years Lee Priest turned pro in 89 peaked in 06 (outlier)
2 years Mike Francois turned pro in 93 peaked in 95 ( retired due to colitis in 98)
7 years Nasser turned pro in 89 peaked in 96
2 years Dennis Wolf pro in 05 peaked in 07
7 years Kai Greene turned pro in 99 but first pro show wasn't until 05 peaked in 12
9 years Shawn Rhoden pro in 09 peaked in 18
10 years Curry pro in 09 peaked in 19
8 years Ramy pro in 2012 peaked in 2020
What I find amazing is that guys from the peak of bodybuilding reached their peak on average of around 6-7 years from the time they turned pro!