I have two weapons, (Beretta 92F and SW 3914) with PT Bar Dot sights. The tritium vials in the 92F were installed in July of 1990. They are still useable. The vials in the SW are about 5 years newer. Sent only the slides, the vials were installed in the existing sights and had 2 week turn around both times.
I will buy my next night sights from them and like Erick, I can't recommend them highly enough.
Jeff