I did it once and yeah they don't work for crap.
I tried with a free sample of Glow-on. http://glow-on.com/
The guy that was selling this stuff at a different board had all these wild clams about 8 to 12 hours of usable light from these sights.
I put my pistol with painted sights on it out in direct sun for 8 to 10 hours. I got maybe 3 hours at most of light from the sights and maybe half of that was usable.