How often do HW wireless sensors need battery changes?

if i am out of town and a battery on door sensor show low, will the system stop working if the battery dies?

Thanks anyway

Once you install a new battery the sensor should start working again.

What happens if I didn't replace the battery in 30 days? How to I get the sensor working again?

The magnet gap shouldn't affect the battery life. If you can install it at the 90 degree angle and the sensor still reliably faults and restores, then it should work fine.

Will the distance of the magnet to the sensor affect the battery life ? I understand ideally the magnet should be place parallel to the sensor within the two markings on the sensor. I'm using the 5820L, my window frame only have 1/2" for the sensor to stick on. However, the Milgard window frame edge has a bevel ending. If I stick the sensor on to the frame only 1/4" of the tape is stick on to the frame, the other 1/4" doesn't get stick because the bevel edge. It's not quite secure. The other choice for me is rotate the sensor 90-degree, stick in onto the window inside wood frame. But then the magnet will be 90-degree to the sensor, instead of parallel to the sensor. I still can place the magnet in between the marks. But it's 90-degree from the sensor instead of 0-degree compare to the regular installation. Does it really matter? If I want to do the 0-degree parallel installation, I would need something to fill up the gap from the bevel to the sensor. But I don't know what to use to fill. What is a best way to do it ? What is the best for battery life ? I don't want 6 months down the road, I need to remove all sensor and reinstall because the poor battery life.