Most newer equipment has slow start circuitry that dramatically reduces the on/off cycling damage possibility for high current amps. So, that really isn't an issue anymore.
Other than that, heat is the enemy. Running equipment 24/7 will reduce the life expectancy of any equipment. Auto manufacturers and dealers now tell people that oil of today is substantially better than oil in the past so time between oil changes can be lengthened. While that may be true. It is still better to change oil every three thousand miles or when that oil appears dirty. Why take chances with expensive repairs.
Some manufacturers want return customers.
common sense is a necessity.
Tube equipment and especially tube amps. I'm turning off. Tube life is typically 2000 hours for power tubes and those suckers are expensive. Unless the amp has some sort of standby circuitry that lengthens tube life.
I learned my lesson so I turn my equipment off after use and turn it on when I come home.
I came home a few years ago to a house smelling of burning circuitry. My Krell KBX electronics crossover has no on/off switch and is always on. Well, some circuitry started to fail and burn.
Well lesson learned. When I'm gone, the equipment is off. My system sounds great after 30 to 40 minutes of warm up.
enjoy