The mattress instructions stated is supposed to sit for 48-72 hours once opened. As we didn’t have anywhere else to put our old mattress, we decided to sleep on this one after about 12 hours of it being out of the box. The first night we were discouraged, as we expected the bed to be more firm. The second night it was much more firm but still not 100 what we wanted. We decided to give it one more night. Once the 3rd night arrived, the mattress was perfect! Medium-firm (a little more towards firm) and once you lay in it it forms to your body and relieves pressure points. We now wake up with zero back pain! This is just what the doctor ordered! We have had the bed for 2 weeks now and still, my husband tells me how much he loves this new mattress! Definitely recommend!