In reply to Jordangask: have used them for a few years. They last a couple of years but need to be put on carefully and in areas not prone to heavy wear.
I would have thought decent electrical tape would have lasted longer?
I've found them to be very robust, none of mine have needed replacing. I suppose it depends on how much you use your gear, but even the tag on my belay crab, which gets used 2-3 times a week, has lasted at least 2 years.
Mine don't get an awful lot of use but have lasted very well. Even got a couple of krabs returned when I didn't even know where I'd lost them. That paid for their use.
Had mine for nearly four years of constant abuse incl winter and alpine and nearly all still on and legible. they have paid for themselves twice over in bits of gear that have been returned. I dropped a DMM Boa on the abseil from Savage Slit last winter and six months later it arrived back in the post!