I don't see how 40 min could be enough. I find with the wrong mattress my back starts to get sore after days or weeks, and I've bought "100 night guarantee" mattresses that started to sag at about the 101st night. It's very hard, at least for me, to make any kind of quick assessment. I'd happily pay a lot but I have no idea what to buy and no confidence that what I do buy will actually last.