How long daes it take your gear to warm up?

My tube amp/pre takes about 30-45 minutes to shine. The effect is pretty noticeable too, during that time.

My tube headphone amp takes about the same amount of time, maybe a hair less, to sounds its best.

I was once told by a manufacturer not to leave solid state amplifiers on all the time, as it is bad for the capacitors if the amps sit unused for long periods while on. Is there any basis to that?

I think the longer my SS amps stay on the better they sound...so over 4 hours is good. Hard to say about the cdp and the tubed pre amp. I don't want to leave that tubed pre amp too long since those early 60's NOS tubes are expensive.
I have a friend that tried leaving his big Levinson amps on all the time until he got his power bill..then he stopped that practice.

Sounds very good at the start when cold, just a touch thin and a slightly compressed soundstage. Sounds excellent after about 45 minutes running music at low volume, and then a slight improvement over the next hour or so. I leave all my solid state gear off when not in use. I would feel uneasy leaving it on unattended for long periods.

30-45 minutes for me...a combination of tubes(pre and amp) and a SS amp on the bass in a biamp configuration.
I usually power up and let it sit for 5-10 minutes before un-muting the pre.
It really 'shines' after 90 minutes.