C-3 #23 still doing it all for me. This summer my C-7 will probably celebrate its second anniversary still sitting unplugged on the shelf waiting for the C-3's retirement.
My C3 (not numbered) is rock solid 99% of the time... get the occasional Alexa issue, some random light won't turn off (they always seem to turn on just fine) but that's about it
No C7 in my future unless (not until) the C3 dies, then I will also look at replacing my legacy ZWave (non plus) switches/outlets...
Just about finished converting my C-4 (voted as such) to my new C-7 with a few Z-Wave devices left. Was tedious but worth going through my network with some cleanup and am now fully protected via the Hub Protect program.
I have a C4 installed in 2 separate locations. Both are still running strong but occasionally become unresponsive and need a reboot or power cycle to bring them back to life. I've been thinking about replacing them with C7s but am not looking forward to moving devices over.
Theoretically your devices should just continue to run until the internal drive fails or some fun electrical thing happens (like on mine). This is the "miracle" of actually owning the device you paid for and not Amazon/Google/Apple/Microsoft/Meta-FB etc.