How long do Tritium sights "last"?

[cass]

I had a set installed on a Commander about fifteen years ago. They stayed visible for about three years, then got so dim they weren't noticeable. Too expensive for what I got out of them.

 

[Mickey D]

I paint my sights with Radium. It's a really good sourse of illumination in darkness and has a half life of 1602 years.

 

[Spotteddog]

Yeah Mickey,
Just don't moisten the artists brush by licking it, and you'll be just fine!
(Elgin Watch Co. employee instruction manual)