Batteries are the only problem with the G&P Aimpoints. They seem to drain battery even not being on. I have 3 G&P aimpoints and a Guard aimpoint. I once left the G&P and the Guarder for a year when I went to work off island here and when I cam back the Guard still worked and the G&P didn't even though they were both off. In the years I have had my G&P's and Guarder the G&P's go through 3x the batteries the Guarder does. Don't know why this is... but they can't be beat. I have had them on AEG's, .22's, 5.56mm, and even the recoil of .308 and all 3 of mine still work.