Calibrating for filament

How often do yo do this?

For the most part, my prints have turned out acceptable for my uses, but I would like to fine tune it a bit more.

New Vendor? New type (PLA, PETG, etc)? New Color?

Once set, how often to re-calibrate? When issues start to arise? Months between orders?
I have seen comments about folks re-calibrating some tests on every new roll. This seems to be an enormous waste.

Humidity in my house generally doesn't get much above 35% (maybe 40% during a rainstorm) and usually hovers in the mid 20's, but I am going to get a dryer to see if that makes much of a difference.