To get back to the point of the thread, I have a Dell Quietkey that I've used on and off now for 25 years, mostly off, but I do occasionally whip it out still. I have an ancient Dell Bigfoot that's fine as well. These are the only long term use keyboard I have that haven't developed issues.
My Model M developed some kind of membrane problem over the years and I had to send it into Unicomp.
My scissor switch keyboards have died due to the scissory parts going bad. The S keys used to always die on the cheap replacements I bought between 2004 and 2010 and I don't know why. I have probably had 10 rubber dome keyboards go on me over the years for no obviously discernible reasons.
I don't, however, consider it to be a rubber dome problem, but a cost problem. I would simply buy the cheapest keyboards I could find and they all sucked butts. All the expensive ish or OEM rubber domes I've had prior to 2010 still work and are fine. The keyboards my parents have used on the other hand in the past 10 years, they've all died and been replaced with $30 Logitechs. My dad swore by Logitech, and I understand why. They make a good reliable product for the guys who don't care that much about keyboards, and for some even who do. Every Logitech he bought still functions. He used to just buy new ones because he liked buying stuff.
Anyway, so since basically the least expensive mechanical keyboard you can buy still costs $40, you're getting way way better build quality than the $2 rubber domes people go with.
I don't think that a Leopold is going to last longer than a $50 board in any practical reality, but when we start to get into vintage keyboards, we can see the build quality really play a factor.
I use a keyboard made in 1981 on the regular. That's 40 years old. I hope to still be using it in another 40 years. Genuinely. For most of the guys asking "hey should I buy a mechanical keyboard?" they're not considering what they're going to use when they're retired, so again, I don't think there's a huge practical benefit to them. But for me, there is.
I want a board with longevity, heritage, mainstream switches, and excellent service options, because I want to use the board when I'm 50. That's part of the reason I use Models M. I'm always going to be able to get those keyboards and as long as Unicomp stays in business another 10 years, I'll probably still be able to get them in good working condition until I die.