If you look at 3M's data sheet, they say they only last 6months from the date you remove it from the sealed package.
That is just the shelf life once you open it. The spec sheet also says it will absorb from it's environment even when not in use, meaning it can have a significantly shorter actual life while in use.
I've seen some spec sheets that suggest for pro car painting use, that these type cartridges are only good for about 48hours of actual use.
This is why I disassemble my mask after every use and store my cartridges in a sealed ziplock baggie in between uses.
Your health is nothing to play games with, so if you can smell anything while wearing that mask, it's not working. Mine totally removes the odor while in use. Oh yeah, and wear it tight, you'll know you had it on right when your wife laughs at the lines it will leave on your face.

EricV