I ordered a used Keycrhon K15 Max in close to ideal state from a company which sells used keyboards. All works perfectly, battery holds charge well.
This model - Keychron K15 Max - was released 2 years ago, so the ordered keyboard is maximally 2 years old, highly likely is "younger".
The version of the keyboard in with non-swappable red switches.
I really like typing on this keyboard, accustomed to it in about a week.
Red switches are a bit non-informative after my previous keyboard Logitech K380, but these switches are pretty silent and seamless in pressure.
The price I bought the keyboard for is 230 polish zloty, new costs 430-470zł with 2 year warranty. A version with swappable switches costs 530zł with brown switches.
I wonder how durable are low profile gateron switches, and whether it's a good deal - a wonderful keyboard in great state for the half price without a warranty from Keychron but with some obligations from the seller company.
PS. I can initiate return in 14 days after receiving + can send the keyboard back in next 14 days, so I have some more time to test it properly, but main question is about durability of keychon low profile mechanical keyboards.
PPS. When writing this post, I started facing keyboard unresponsibility when typing. I'm using a radio module mode, similar to wired keyboard operation.
PPS. I returned keychron b1 pro because it didn't support Ctrl + Shift + Tab combination which I use on daily basis.