Is anyone else frustrated by the lifespan of dog beds?

Granted I have a lot of dogs, so I have eight dog beds to mess with. I can't buy the round foam ones with a fabric cover, because my dogs KNOW there is fun-to-shred foam in there somewhere, and they WILL get it out.

I normally buy the ones with an outside cover, and an inner bag filled with stuffing. But, one of two things happen fairly quickly ... either the zipper breaks on the cover after one or two washes, or the stuffing gets compacted and nasty.

I seem to spend a small fortune replacing dog beds. Does anyone have any better solutions? And does anyone have any ideas for an inexpensive material to re-stuff them with?

Thanks!