One of my three fuel caps appears to have an O-ring which is stiffer (header tank) than those on the wings. It closes ok but the tab no longer sits flush with the cap surface. I'm wondering whether the O-rings which came with the original kit are now beyond their useful life. (not from flight time but build time)...
From your experience, how frequently should they be swapped out in the field?

Angier Ames
N4ZQ