How many surgeries should you have in a lifetime?

Doesn't matter: Surgery is performed for medical necessity. There is no limit if you need the surgery you can have it unless there is a medical contraindication.

Hopefully none: Hopefully, a person is lucky enough to be healthy all the time and never need a surgery. There are many surgery types, all the way from removal of a small mole to removal of entire limbs. A person can have as many surgeries as his medical conditions require. If he gets to a point where no surgery will improve his quality of life, then his time has come, and he should have no more surgeries.