Great American Pellets

I've got about 15 bags of Great American Pellets left over from my first heating season with wood pellets back in May 2011. During Winter 2011-2012 i experimented with Turmans and love the low ash so this year i bought Turmans. Every once in a while i'll toss a bag of Great Am Pellets to use them up but they cause the house to smell smoky. As soon as i go back to the Turmans the smell is gone. Weird. Do pellets go bad?

They are stored in my basement (which gets no water in it anywhere) with a piece of cardboard between the first row of pellets and a tall pallet between the cardboard and the basement concrete floor.