We have had all sorts of trouble with our bedroom smoke detector, even after replacing the original one with a new model with a 10-year battery. I think minor environmental things like dust and such trips it off. We also can't climb ladders for a variety of reasons, so their position is a maintenance nightmare for us.
After our third episdode of false alarms (always in the middle of the night, of course), we paid someone to remove the installed smoke alarms and cover each hole with a small plate (same size as for a standard light switch) and installed new smoke detectors just over the door (also with 10-year batteries, ran us about $18 each). I can get on a chair to service those if necessary. So far, we haven't had a false alarm.
We have given up a small amount of safety by not placing them in their ideal location, that is, at ceiling level. On the other hand, if one of them goes off, we'll see if there's a fire in the house. The old ones were such a problem that when they went off we stopped checking for fire because we knew it was a false alarm.
We also have a high quality fire/smoke alarm installed and maintained by ADT as part of our security package. An additional benefit of that alarm is that if goes off, ADT notifies the fire department right away. We have never had a false alarm with that unit.
I hope this helps. Like you, I don't know why the bedroom fire alarm was such a problem, I'm sure it's something environmental. Ours too was a nightmare.