Someone mentioned this so thought I'd make it.
How long have you kept used diapers in your room?
As for me, the only box left in my closet is the one that's been there for a few years now. I forget exactly when I started putting them there, but I do know that this was back when I could only get Depends at like K-mart, etc. So, I'm gonna take a guess and say it's probably been a few years. Don't quote me on that, as it's somewhere between 2 and 4 years I think.