Re: Key Clamps - Why the controversy?
I like to use key clamps when setting new pads but don't advocate their use for everyday purposes, though I might consider using them for airport handling.
As far as the springs losing tension, think of the keys that are naturally sprung closed. After 80 years, those will still spring, so I think that's someone's unsubstantiated opinion - not a fact.
It's great you are using a pull-through swab.
So unless your horn is getting really tossed around, I wouldn't worry about using key clamps.