Hey herbyguitar, hard to say, depends what you mean by lose
. My initial thoughts are:
Tubes - they go off over time but with use, not just sitting there. Anyway a new set of nice tight tubes never hurts and often sorts it out.
Caps - the electrolytic capacitors dry up over time (with or without use) so the MP1 noise mod is well worth doing and tends to "tighten" the unit up
MDRT - this replacement transformer (available from MJMP) really makes a difference. It makes sense to do the noise mod and MDRT at the same time as, IIRC, the MDRT mod requires some cap changes on the tube board
Rear jack mod - this replaces the front and rear input jacks, the front jack gets the most wear over time and needs to be replaced from time to time.
My friend MikeB did these mods and the unit is now like new, but a bit better from the MDRT. Tube wise, he's using a Boogie STR (so a JJ) in V1 and a Mullard short plate in V2 (or is it the other way around ?)