hard to say on the life of o-ring, I have not heard the o-rings leak over time issue, if any very isolated. Overtime a crust of coolant develops around the o-ring sealing it of. I had to use a brio pad to clean the pipes when I did my VP, I resued them and that was 25000 miles ago and no leaks what so ever.

My wild guess, is the leak on gaskets is more commons, for example the coolant manifold gaskets in the back of V8 is spec to be torque rather low so vibration can loosen those 3 screws and leak develop. I use loctite on those screws cause it's a bitch to re-tighten once the intake is back on.

as far as VP, mine was not even leaking at 65kmiles, I misdiagnosed pinch o-ring on WP side, should have pressure test the problem but since alot VP is leaking I thought mine was too.