I own a couple of these burlap bag targets. Made in Tacoma. . . .
The Texas targets are made from a poly - burlap which won't rot like regular burlap. If you put just non-biodegradable plastic in them, you can leave them out in the weather year round. I would think carpet would mold and rot in a short time.
I wonder what the prices are and whether you can pick them up at the manufacturer? I'm close to Tacoma, although avoid going in there like the plague. Anyway, I've already bought the poly cubes and I think they will last me as long as I need them.