Worn valves that no longer hold compression?
Worn chops that no longer hold compression

Probably not the brass.
Daniel C. Oberloh
Oberloh woodwind and Brass Works
http://www.oberloh.com
Yes.Lew wrote:I've heard this too, and it's nonsense. Valves wear and slides lose compression, but just aging the brass, or playing too much will not render a brass instrument less playable.