I pr'd at 1500m, mile, 3000m, 5000m, and 10000m as a college soph in 1989, then got tendonitis in my knee and couldn't run for 15 years. I came back to break all of those pr's except the mile.
1500m (1989-2008)-19 years, dropped it 2 seconds.
mile 1989- --got within 2 seconds of it in 2009 but haven't gotten it yet and there are not a lot of track miles down here
3000m 1989-2007 or 2008 ran about a second better a bunch of times before dropping it another 12 seconds in 2009: lasted 18 or 19 years
5000m 1989-2008 dropped it 16 seconds a few hours after getting the new 1500m pr lasted 19 years. I'm still hoping to drop this more this month or next month.
10000m pr 1989-2007, lasted 18 years, dropped it by 1 second, then a couple years later, dropped it by about 90 seconds, and then another 13 seconds last year.
There's always hope.