How do I know my filter is still running ok? can it wear off in just a month?

How do I know my filter still runs fine? If you are getting smells outside the tent then it is not running fine. High umidity is a factor? Yes, high humidity reduces efficiency. The water vapor molecules in the air block absorption sites (pores) in the carbon. When those pores get blocked by water molecules smell's cannot enter and get trapped in the carbon. You can remove your filter and bake in the oven for 2 or 3 hours on low temperature to drive out the moisture. If your filter has plastic make sure to use a very low temperature. Getting a "smart" fan or adding temperature and humidity controls to your fan will help by only running the fan when it is needed.

Humidity will shorten the life of a carbon filter. I would either buy a bigger filter or control humidity (below 60% is optimal for filters) with a dehumidifier or air conditioner.