Mike the stuff at the store also doesn't have fat, I did a lot of reading on making Jerky before I found this guy. It is the fat that makes the Jerky go moldy because it holds moisture.
The fridge definitely helps though, I was at around the 2 week mark when I started seeing mold without the fridge, with the fridge it goes for a much longer time.
Also definitely keep it vacuumed sealed until you are ready to eat, that should help a lot too.