I agree with most comments above, we will never know if the gun would have lasted until the end of time or let go on the next round. And anyway, that type of failure is not particularly dangerous, as Craigd says above, the shooter just needs to stop shooting.
The reason I reproof is partly because I can but mainly because I get asked unbelievably uninformed questions at every show I exhibit at, demonstrating the level of ignorance amongst the gun buying public.
Also a lot of people in the USA reload which is an excellent way of producing mild cartridges for vintage guns. It is also an excellent way of producing proof charges if you don't know what you are doing or are distracted by the dog peeing on your foot!
I have no way of knowing who is going to land up shooting my wares, their level of knowledge, stupidity or if their dog is house-trained.
I also can not be sure that someone isn't going to block their barrels with a 20g shell or a wad of snow and turn their carefully selected recipe into a proof load.
As Stan says above, its about going the extra mile.
