We see dozens of customers in our showroom every month who have bought a memory foam mattress and can't live with it anymore either because it makes them hot at night (even models that are using cool gel) or because it becomes prematurely non-supporting.
We always suggest trying a latex mattress because virtually no one has every complained about heat issues and because they ALWAYS keep their shape longer than any other type of mattress. You will be happier longer if you choose a latex mattress you find comfortable.
I say this while admitting that I have slept on memory foam for 15 years but also admitting that I have replaced my mattress every 3-5 years because memory foam does not truly have that great a memory and loses its ability support me.