Many manufacturers of high end amplifiers recommend just leaving them all the time. For example, I recently purchased some custom Odyssey Khartago Mono's and the owner and chief engineer, Klaus recommends leaving them on all the time.
Not sure this is as important with integrated setups like a Denon though. I don't leave my 2805 on all the time.
There are two schools of thought on this subject, and I really don't want to get that debate started again. However, I will follow what the manufacturer states for my equipment to keep the large capacitors charged, etc.
