need to break in equip after prolonged non-use?

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

If any amp or preamp has been sitting for a while, the filter capacitors in the power supplies will have to 'form up' again which can take some time. Until that time the equipment won't sound right.

If its been sitting too long the filter caps can fail. They are not unlike batteries in that regard, but usually it would take several years for that to occur.

I have always found that, yes, it will need to re-break-in, but nowhere near the length of time the first time around.

I asked Jorma Kosky from Jorma Design cables that same question. Specifically I asked him if I hadn't used my speaker cables in 6 months, how long would they require reach the same level of break in again? This was his response -

When the cables have not been used since then, they need a little time, I can not say how long, it depends on so many factors.

The same principle can be applied to components. You certainly don't go back to square one, but I would think your gear would need 1-2 weeks regularly playing a signal to be refreshed.