Whats the downside of leaving ones amps on allways

Could start a fire.

Jdwek - when I bought my first Bryston amp back in 1989 I remember reading something (in the manual) about leaving the amp on all the time as it ensured that the amp was in its optimal operating condition when "warmed up" - they advised that when the amp was sitting idle it was drawing the equivalent power to that of a 100 watt light bulb. Is that alot - I guess it depends on what one pays for power...

The downside, is the wear on your amps occur, even when, you are not listening, and the cost of electricity. The wear, is minimal, with solid state gear, but with tube power amps, it will reduce the time, of tube replacement, to approx. 1/4. If the tubes lasted 2 years, listening 6 hours a day, then they will last only 6 months, listening 24 hours a day.
The electricity costs, will vary, with type, of amp. Class A, will definitely add considerablely, to the costs.
The cycling on, and off, is definitely hard, on gear, both solid state, and tube. Manufacturers, had added a lot of features, to minimize this, such as "softstart", to gently apply the inrush currents.
I use tubes, on the midrange, and high frequency, and solid state, on the bottom. I shut the tubes down, whenever I am not listening. I leave the solid state on, continuously. Lightning strikes, is the only reason, I shut it down, and unplug it. I even use, a little trick, of coiling the last 2 feet, so if a huge surge hits it, while I'm not home, it will melt the cord away, at the coil, and hopefully prevent the juice, from getting to the amp.

I hate to leave any piece of electronics on for an extended period - especially if I'm gone - I have a McIntosh MC-2100 amp and it gets fairly hot(enough that you can only touch the hot spot for a few seconds) - it doesn't have a power switch, so I plug it in to a power strip and shut it down every day - I don't think it makes a difference in the sound that much - but heck, I'm over 50, so take everything I say with a grain of salt.