Zac67 wrote:
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You could just use that rule for not-in-use/stored caps with, say 25°C, but I think they age a lot slower when not in use.
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Hmmm - some years ago I repaired an old radio (build somewhen in the late 1920ies), that a friend had found in his attic.
It had two large electrolytic caps (like the starting capacitors in washing machines) that were defunct and caused the radio to grumble when turned on.
It took me nearly half a year to find replacement for those beasts, and the salesperson recommended to switch the radio on at least every few weeks to avoid the electrolytic caps to dry up again (that's why the old ones were defunct)...
