Alarm sensor battery run down without warning?

My wife mentioned that on trying to arm the alarm it was warning about sensors requiring bypass. On investigation I could see that it was one of my motion sensors. So it apparently just stopped working having got to no battery? I have a lot of sensors, am I meant to wait for them all to give up functioning or go through each device individually to check its battery health ? I had expected the app would start to warn me and say “x devices are approaching low battery” as a prompt to replace. Presumably sensors could just stop functioning while an owner is away on holiday which would not be good at all in terms of the products primary function ?