This is my first time buying a mattress/bed. I am looking for a double mattress for my husband (5ft 4", 60kg) and myself (used to be 5ft 4", 60kg... but currently pregnant). We are people that tend to use products well past their expiration. This is partly out of avoiding contributing to landfills and getting our full money's worth, but also partly because life is busy and we are lazy. Keeping this in mind as I research and then buy, I am wondering what mattress you might recommend that has the best probability of still being 'ok' in 20-40 yrs time. Husband says he thinks he likes medium firmness. I am not sure for myself and frankly, don't trust that my past or current opinions of comfortable sleeping arrangements will be valid in even the short future. Thank you for any advice or suggestions you can provide. Best wishes.