I’m glad they have been working for you, but this has not been the community experience. Literally dozens of people have reported reliability issues with keeping these devices connected to the network.
And it has been verified by SmartThings engineering staff that the Xiaomi buttons are not operating completely to the zigbee home automation profile, which is the one that SmartThings uses.
One of the main issues is that these devices have different behavior when they’re communicating through a repeater other than their own brand. This is one of the reasons different people report different experiences, particularly with regard to reliability. It’s not a matter of having a strong mesh-- for some people, the stronger the mesh, the worse the Xiaomi behave because they keep using other repeaters.
See any of the existing threads on the Xiaomi devices and you will see discussion of drop off issues.
People continue to use them because they’re very inexpensive, but they were really designed to work with their own Gateway and they are not 100% compliant to the standard. If you going to operate them within 1 hop of the hub, and the hub has enough child slots, you may be OK. Beyond that it can get quite tricky.