Do Smoke Detectors expire?
 

I have a wired smoke detector just outside my bathroom, and when i started doing some soldering, it started going off... there was very little smoke from the flux. There is another smoke detector in the hallway, that is wired to my house alarm, and it is not nearly as sensitive. After about 30 minutes of soldering, the house alarm detector had still not made a sound.

I don't think smoke detectors expire but, I do know that CO2 detectors expire after 7 years. The odd part is that they don't put an expiration date on them. They only list the date of mfg. and assume you know to change them after 7 years if you are aware of the fact that they don't last forever.
Regarding smoke detectors, I would think that if it gets a whif of soldering smoke it should go into alarm. They don't alarm for just any kind of smoke though. Cigarette smoke will not activate them.

In the big picture, better too sensitive than not sensitive enough. Eh?

10 years NFPA

To be more clear, yes smoke detectors have a life span and should be replaced in 10 years.