This thread is turning into one of those ...
* Sometimes you really need to, sometimes you don't.
* Powered up 10 years ago means it's probably OK, if the thing was NEW
10 years ago; if it was old then it's ancient now.
* That said, testing is "easy" on ferroresonant S100 chassis
and hard on smart-ass switchers with fixed loads; you need OEM
data to test.
I think a good rule of thumb is, you need to know when to test,
and when you might reasonably 'get away without it'.
As always, knowledge, information and luck is required, and we
all make judgement calls, right and wrong.