Thinking/researching the same thing for multiple weapons. There are sights that have both, that is fiber optic for daytime with tritium for night. Yes, tritium should last 12 to 15 years. Be sure to read all the reviews you can, evidently, not all tritium is created equal. Some sights are brighter than others.
So far, I have purchased XS sights (tritium) for my AR15's (front post) and have Troy folding battle sights with tritium for the rears. I like the set up very much. Excellent both day and night. Front and rear are green, no problem lining them up.
I have not purchased any others yet. Still researching.
Definitely sign up for the concealed carry class!
NRA Life Member