? Memory Foam Mattress Question

When I bought a Tempurpedic memory foam mattress (years ago), it said not to use an electric blanket. I think it even said such use would void the warranty (as if they would find out; as if a mattress mfgr. would honor a warranty in the first place).

I did use an electric blanket, and I still do, with no-name memory foam that I now use. The heat does make them compress more. I sleep better in the summer -- with no electric blanket -- than I do in the winter.