As a counter anecdote, in about ~15 years of using mechanical keyboards I've never had one fail. I had a daily driver for 7 years that was good as new when I eventually gave it to a friend.
Couldn't agree more about the other two points though. To go along with your second point I would also strongly suggest looking for a keyboard that is hot swappable. You can use a switch tester and all that, but only actual experience will tell you what you really want, and I think very few people end up sticking with the first switch they have. A hot swappable board will let you alter the switches without replacing the whole device.
I concur with the last two points as well. It is a bit annoying, but I recommend getting 3 or 4 of a single switch to put in a tester to mimic "real typing".
I am a strongly believer of smaller is better, my daily driver is a 48 key ortholinear board. I use a 60% from time to time, and it feels gigantic. I can't even imagine going back to a full 104 keyboard.
Couldn't agree more about the other two points though. To go along with your second point I would also strongly suggest looking for a keyboard that is hot swappable. You can use a switch tester and all that, but only actual experience will tell you what you really want, and I think very few people end up sticking with the first switch they have. A hot swappable board will let you alter the switches without replacing the whole device.