I should have also mentioned that we use a Travasak. It eliminates the need to put sheets on the mattress. It's sort of a fancy sleeping bag with sheets Velcro'd into it. It has a summer side and a winter side. The material is very comfy too. They sleep very nice and are quite popular, we love ours, though I must mention that some people dislike them.
When we bought ours we were told that the company had been sold and the new company wasn't interested in making the product. There are other companies that make a similar product.
Neal