Time for the classic coaches conundrum (thank you, thank you, I think it's a nice piece of alliteration as well).

You have a student who always takes their backswing to the same place, but adjusts their acceleration (or deceleration) to control distance. They consistently leave their second putt within 4 or 5 feet, and hole out occasionally. They two putt from almost anywhere on the green.

Do you take the time to teach them the proper pendulum stroke, or let them be?