*this is a comment to continue the conversation from "Bladders from Dr. Tuba?" about when you should replace your bladders.
"pacoz said..When does one actually need to replace the bladder? Obviously when it's damaged, but other than that, when it doesn't hold pressure over the course of one session or simply (like maintenance) just after certain hours of usage?
Asking because I never replaced a bladder until now and some of my wings are pretty old already."
Replacement is an unknown variable that is probably untracked by most but here's my most recent data:
At some point in my last session my 3m started to leak on the water. During inspection at home the bladder burst. Total miles recorded on that wing is 1,815 over the course of 1 year.
Upon inspection of the failure point I thought the popped location looked like it was worn abnormally. So, I pulled the bladder of my 4m to compare and found the exact same wear pattern in the exact same location.
Here's an image of the 4m bladder. You can see the material is fatigued, it looks almost exactly like when you try to push your finger through a plastic bag and the material gets stretched, deformed, discolored. This spot is smaller on the 4m than the large area that was fatigued on the 3m and failed. The 4m has 880 miles on it over the last year.

Normally I would never pull my bladders out to inspect them and check for wear. This is a rare occurrence and only happening since I was unsure about the failure on my 3m. I'm replacing the 3m bladder obviously because it burst. I am also replacing the 4m bladder because we can see that it will, in fact, also burst at some point. I'll keep the current 4m bladder as a backup after installing the new bladder so that I'm never without in a failure.
Some riders might just push it until it explodes but the nature of my riding, being far from home, (my last session on the 4m was a 45 minute downwinder and then upwind 30 minutes back), means extreme swim distances if I don't want to hitchhike make replacement an easy choice.
I have never put so many miles on my wings. Normally I've replaced my wings after a season to keep my quiver fresh. With the AA wings though, they are so light, stiff, and the canopy/frame is such an amazing material that I don't intend to get rid of them in the same timeline as my past wings. I've currently set an arbitrary 5000 mile retirement timeline on them. As such, I should probably pull my bladders out and inspect them every fall and buy replacements for any that show obvious wear spots. Just like changing the fluids in your car!