Sometimes they expand with age and begin to bulge and the tops look somewhat rounded. These would be bad. But the age of these caps should be replaced regardless. Better safe than sorry.
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If the unit has been in semi constant use, your cpas should be fine. You can try and reform them if they look good by bringing them up slowly on a Variac. I’m not a fan of recapping just because the caps are old. If they are defective or measure poorly then yes, replace them. Once they start to dry out they bulge and the cans will begin to leak.