The receiver position will also affect the battery consumption. Check the power consumption with the remote at rx/tx with the power saver off at 0ft, 300ft, and 600ft. The further away from the car, the more power the remote will use to maintain communication. When you go out of range, the remote stays at high power searching for the car every few minutes which will also reduce power.

Its been a while since I did the checks but heres a ballpark of what you should get:

.75ma at the car
1.25ma ~300ft
2.15ma ~600


I did my tests on the 791 05 series alarm with a Duracell 1.5v AAA battery- the remotes may be more efficient now.

Now that I do the math it looks like a much shorter than 6 month life span but Ive never seen 1 month changes on any of my installs.