The biggest mistake currently being made with the dog beds you see in the store is they aren't washable. Yes, the cover is, but the cushion inside isn't. Eventually it gets dirty and starts to stink, and the bed gets thrown out.
I solved the problem by buying quilt batting, and folding it up, and using it to stuff the bed. I remove it and put it in the washer with the outer cover when washing the bed. Eventually, it falls apart, and has to be replaced, but it's quite cheap to buy!
I don't know about other people's dogs, but mine vomit, one of them bleeds on the bed when in heat, and my old girl occasionally poops in her sleep. (She turns 14 in January.) So, yeah, something washable is a GREAT idea!