My G3 XR-15 is still going strong after over 5 years. I'm hoping for 2-3 more. Of course, I'm not taking PAR measurements and comparing them to new. But with mostly softies, I'm much less concerned about minor degradation. Corals are growing very well, BTAs all have great bubble tips and continue to split, no change in algae which I hope means no shifting to red. No issues with power supply or control functions. I haven't changed any settings in 3 years now.
I have four G4pros and they’re still functioning fine after 7 1/2 years. I am sure they’ve lost some PAR, but neither I nor my livestock seem to have noticed. I feel with these, as I do with my VorTech of similar vintage: please don’t fail because I have no desire to be afflicted with mobius.
5 years is a good timeline. They can last longer, but some also fail just a few months out of warranty.
For me, degradation would not be an issue - you can always turn them up since nearly nobody uses them at 100% anyway. They usually have board or complete failure issues.
If you like them, then start to buy some slightly used ones when they get cheap. Just saw a pair of Gen 4 xr30s go for $180 locally and a fellow bought them for backups.
Does anyone perform any maintenance on these units? All I do is vacuum off the dust build up occasionally on the top of the unit for the fan to pull in air. Outside of that, is there a need for anything else?