You say that like it's the easiest thing in the world. We had a great bed for the last ten years but it is done.

Bought a super expensive extra firm mattress... immediate back pain. Stuck it out for a month, no good. Couldn't return it coz we chose wrong...now I have a stupidly expensive guest bed.

Tried one of the mattress in a box companies who claimed to be one of the firmest available. it was a soggy mess.

Returned. Bought another with a less favourable return policy but half the price...my wife hated it so much that I donated it to the local op shop.

Were on our latest mattress now and my back is absolutely killing me.

It's just impossible to know what will work for you. A quick lay down in the shop isn't going to cut it, but I am sick to death of looking. A real shame the company that made our original super firm mattress went out of business.