Heat can be an issue with electronics for manufacturers that cut corners on the quality of their components. The bigger issue is the heating cooling cycle. This will cause expansion and contraction that will damage components. I leave my gear on 24 / 7. Example my old sansui 7070 running in my wife's business has not been turned off for 24 years except for a couple power outages.
heat
i only use my stereo on sundays for 6 hours. i recently started to put paper towels above the air vents on my pre amp tuner and power amp to keep the dust out. i have a mcintosh mx132 and mc602. is this a bad idea? i know heat is the worst enemy for electronics but i don't play it loud anyway!