Need info on vortex viper red dot.

[Revolver Ocelot]

I'm currently being offered a vortex viper red dot sight at a price that is hard to ignore, and was considering purchasing it to have mounted on a pistol.

I have a couple questions though, what kind of battery life can I expect out of the sight if I were to use it everyday, and how sensitive are the buttons on the left hand side (wondering how easy it would be to accidentally actuate them while the gun is holstered).