I've had a Princeton Tech Pulsar II for years. It's currently in my PSK - I just fished it out and it worked fine. I don't EDC it any more because I found the switch could lock on and run the battery down, but that's a fault of that particular model, not coin lights in general.
For EDC I now have a Photon Freedom. This has a better design - much less likely to stay on unnoticed. I usually put it into signal mode, but I'm currently experimenting with leaving it in the default mode because it is so hard to switch on accidently. I can't remember how long I've had it, many months if not over a year, and it shows no sign of falling apart or going flat.
If coin lights in general are as poor as you suggest, I doubt Doug would recommend one
here .