I ran my track bests in college for the most part. I did however find a way to schedule training around my two jobs (full time desk and coaching HS track/XC) for roughly a decade. I kept chasing those PR's and always thought I was pretty close until probably 34-35 years old.
800 - Never really tried to beat, but got ~2 seconds off
15/mile - came within half a second at 29
3k - half a second at 29
5k - PR at 29
8k road - PR at 30
10k road - never tried
The 5 years after 29-30 I was always super fit and ready for a good race, just needed to have the venue to do it, I just kept getting hurt the instant I got into peak form (recurring injury). At 31 I had one of my best 1500s and was close to qualifying for the trials. At 34 I had the best season opening race I've ever run (4:04 mile) but was hurt a week and a half later and it put an end to everything I'd built for that season. It's riding a razor thin line at that age (when you're doing it as a hobby) between maximizing training and keeping healthy. I leaned a teeny bit too far toward performance over health and was my own demise.
After 35 I realized the PR's I wanted were not going to come. But I was damn close and loved chasing them. And I loved being in my mid 30s (kids, 60 hours a week at a desk, tetris'ing my training in between) taking down 20 year olds with nothing but testosterone and time to train. I really miss all that now but I'm glad I had the career I did.