Smoke detector didn't go off

I have a smoke detector that wired into the house wiring. Replaced the battery in October, and the test button fires fine.

This morning, I left a pot on the hob with the fire on, forgot about it and went out of a room where the door'd been shut into a smoke-filled house. Well, nothing damaged, the pot has cleaned up perfectly, but the smoke detector never went off.

I expect the detector is at least 5 years old, the house was built in 2004 and it might be original. I intend to replace it and perhaps buy an additional battery-only unit for somewhere else in the house, the bad smoke detector is in the main hallway. I am planning on installing the battery unit in a room adjoining the kitchen and replacing the bad detector with a new version of same.

Should you replace detectors regularly? I actually did replace one last year in the attic which is unfinished, but I was doing some work up there and succeeded in breaking the detector there (also a hardwired unit) so I got a replacement at the electrical supply store that was the exact same unit, which is the same model as the one that failed this morning.

Finally, could a problem with the wiring cause the detector not to trigger? The LED light is always on, I would assume if there weren't enough voltage there'd be some indication. And, wouldn't the battery backup matter in this case?

Thanks