I repair electronics for a living and I can tell you that most problems with low power units (not power amps) happen at power up.Its like being thrown in cold water to a person,it can kill you.All of my non- power amp equipment is left on all the time.Also use a backup power supply, surge protectors do not help with voltage sags.These can kill electronics just as well as spikes.My 990 has never been turned off other than for connecting to other equipment. Long live the 990!