My FS 29er (M9000 – 2×11) and my son’s MTB (M8000 – 1×11) have both used quicklinks from new with no difficulties whatsoever. I do this because it makes maintenance so much easier and, frankly, I can’t see any reason not to. Both bikes are KMC, but I’ve also used SRAM in the past and consider them interchangable.
Technically, they are only to be used once, but as everyone knows, this is bobbins. I don’t remove the chain that often, so they just get replaced with the chain. I did remove one from a much older bike a couple of days ago and that fell off almost without effort, so I suppose they can wear out, but I’ve never kept one long enough to find out 🙂