Can an intact shingle be reused after its seal strip releases?

If a shingle has to be lifted for a small repair, I’m unsure when it’s reasonable to put the same one back and when replacement is the safer call. A shingle can look intact but still have brittle edges or damaged nail holes, and pressing it down doesn’t prove the seal strip has bonded again.

How much do age and cold-weather brittleness change the risk of lifting it without cracking it or disturbing the shingles around it? What do you look for at the old nail holes and fastening area before deciding it can be reused? If the shingle stays whole but its seal strip has released, is there a reliable way to secure it, or is that a roofer’s call?