Any amplifier that has a slow start circuit effectively removes the problem of large inrush current cycling. That is why the slow start circuits were developed.
This eliminates the argument about turning the amp on and off and inrush current issues.
Most modern amps have not only a slow start circuit but standby circuits also.
But, as a person knowledgeable in electronics and electricity, I wouldn't recommend anyone to leave their equipment on all the time. Heat is the long term problem with electronics. I have seen many times electronics fry from being on. I have never seen electronics have issues because of on/off cycling.
For example, I have a Krell KBX electronic crossover, configured for my Martin Logan Monolith III speakers. That crossover is built like a tank with a separate outboard power supply, but no on/off switch. Once plugged in, it is always on. Good Idea right? wrong! I started smelling the tell tale smell of burning electronics and lo and behold, some components began smoking. I reversed engineered the crossover and found the problem, repaired it and from that day on, I leave the crossover unplugged/turned off until I need it.
All my equipment is turned off until about an hour or so before I start listening.
Also, I unplug everything when I leave my home for a few days or more.
But, if some people claim that they hear a distinct difference in sound quality by leaving their equipment on all the time. More power to them. I have experimented with this with my stuff and I don't hear any difference if my equipment is turned on an hour before listening vs leaving them on all the time.
A glass of good wine, a good book, and good music and I am good to go after an hour of warm up.
enjoy