Quarq hadn't been around very long - they started shipping in 2008. I can't speak for their units.

SRM has been around for a while. I don't know when the PowerControl 5 ("PCV") came out but that's what I have. Now they're on PC7/wireless. They still sell stuff for PCV.

I bought one new in 2008 (came with a 2007 bike). I bought another one for a second bike. Both are still going. For me it's been batteries, wiring harnesses, and mounts. I replaced 1 crank battery in each and need to replace one headunit battery, still to be done. I am on my 4th? wiring harness, and I have a new one for the second bike (it was disassembled and needs to be reassembled). I lost a few bar mounts so I bought some of those too.

There are riders using older similar units. We're talking 7-8 years old or more. I think they're PCVs. A friend has owned one for something like 10 years, still uses it, I think it's a PCV.