I have
Tuffies and they never go flat or lumpy and they don't smell.
They aren't cheap but in the long term they are a much better option than wasting money on flimsy beds. I do sling covers over them as my dogs prefer them covered but I don't buy the covers from Tuffies. I use cotton towels or elasticated terry towelling cot sheets which fit pretty well.
I prefer multiple beds for my dogs (much more flexible) but rectangular beds like these can be positioned side by side if you think your dogs would prefer to be close to each other.
I'd highly recommend them and I know there are others on here that swear by Tuffies too!