To your questions:
1. Mine stays on all the time.
2. I’ve had this one a year and it is still bright. I’ll change it out soon. Its very easy to do.
3. Holsters are easy to find. Red dots are extremely popular.
As noted, get one that will put the dot on top of the front sight.
It always amuses me that the folks who would benefit the most from a red dot sight are often the most resistant.
My well-funded PD has optics on all issued guns. They qualify with the sights turned on and turned off. They love them.
I’ve shot irons my whole life, and still do. Red dots are a nice addition on a carry gun.
Yeah I’ve noticed the same thing. I heard early and often by many instructors to never stop learning. Never become unteachable and never think you can’t learn from a younger instructor. New stuff is not the answer to all your shooting problems nor is it useless. It’s just new stuff. It may work it may not. I have boxes of stuff that didn’t. I keep what works and toss what doesn’t. But I never look for a replacement to training. You can’t buy skill. You can buy useful tools though. Keep an open mind.