Musical Fidelity A220 integrated amp

The mid range is more focused and instrument separation clearly improves. It seems much brighter when turned on and than after an hour or two sounds warmer and relaxed. I agree that leaving it on would be best, I listen when I get the urge through out the day and evening. 

It's over 20 years old and original, so I'm worried leaving it on always will retire it sooner. 

That's what's concerning because the A220 doesn't seem to have a standby. It's either off or on full throttle.