After 12 years of faithful service, I was told by my LBS that my BB needed to be replaced, as part of a more general rebuild of worn bits & bobs on my bike.
For the first few years of having the bike, I was generally running around in 53x15 as the cruising gear, sometimes dropping to 53x14. Latterly (for the last couple of years) I found myself cruising in 53x17 dropping to 53x15 occasionally (no 16 on the back!). I put this down to advancing years at the time
After getting a new BB - wow! I’m now cruising around in 53x15 again fresh as a daisy, dropping to 53x14 much more readily. I’m also riding more consistently at 90rpm in 53x15 that I was in 53x17. All a bit of a revelation to me.
Which leads me to a question: is there any guidance or rule of thumb as to how long a BB lasts before it loses its “newness” (as opposed to become unusably worn?