An explosively dismantled Enfeld

[RobD]

OK, we all agree we "should be able" to see a deliberately-drilled hole. And it's our own lookout if we don't.
Most of the blown-up actions shown on this forum were those in which metal fatigue or other invisible processes were at work. We have been fortunate to have owned and shot WW1 and WW2 -era rifles in a strong condition, with obvious clues to how many rounds have been put through them. But our kids and their kids etc. may well still be bolt-action enthusiasts, and the rifles will be a lot older - maybe rebarrelled several times... but with pressure-bearing parts which have gone around the block an unquantifiable number of times.
So my Q is: At what point in a rifle's life is it prudent to re-proof? And how is that done? (both in the UK and elsewhere?)