need to break in equip after prolonged non-use?

Bot it definitely will need to be re-broken in after that amount of time.

I read somewhere that yes, but it's easy to find out and will probably vary. I just unpacked my old Audiolab integrated that was out of my system for four years. I only tried headphone output not speaker. Sounded okay, but the cable from the player that I used was not fully burnt-in yet, so I am not sure what was contributing to what. But again the sound was not bad at all.

I have been running a tube amp Music Ref Rm9 in my room since last spring when it returned from being over hauled.
A SS Amp FPB600 was not being used. Just sat there covered - its too big to move.

Couple of weeks ago I woke up the beast. I let it warm up in standby mode for about 4- 6 hours before turning it on.
When I did - I listened for a couple of hours and it wasn't doing it for me. Not the amp I remembered. The RM9 was superior.
So I opened the Krell manual which clearly states by design for optimum performance it should be in standby all the time.

This time I plugged it in and left it for 24 hours in standby. I then turned it on.
Everything that I remembered about that amp came back. This tells me SS depending on design needs time.

My Tube amps experience has been - don't leave them lying around unused for long periods. Use them. But once you turn them on they are performing well after 15 - 20 minutes if everything is ok with the amp.

Cheers