Life span of a Carbon filter

How long should a carbon filter last for mine has been running for about 11 weeks now and is not has efficient. The plants have 1 week left before cropping and I have noticed a strong smell of weed where I have them vented to.

If its only 11 wks old then its defo still got life init, All depends really mate on what brand you brought. Cheapies last for 12 - 18 months so its defo not your filter. How big is your room, And how many plants you got ? How big is you fan and filter ?

I am using a 4*4 tent there are 10 plants and the filter is 5" the fan was a 5" but I upgraded it to a 6" centrifugal fan.This is my first grow so I am still learning any advise is welcomed.

Sounds like you might need a better or bigger filter or the strain your growing is just super dank and you need to add on something like one of those uvonair things like this --> http://www.4hydroponics.com/growroom/air2.asp?ItemNo=uvonair800