The wall sags here, pits there, has spider cracks and an occasional cleft where water from a past leak eroded the plaster. You might find that cracking came from beams flexing or subsiding. Fix it now and you'll fix it again until you repair the underlying problem. You have to get in, tear out the problem, do the hard work and put it back again. If you own an old house like I do, you know there is no such a thing as putting anything back easily because nothing is square.
Houses are like people.
They bulge with age in the wrong spots. I believe PR practitioners should work weekly with their hands. It's a good reminder.