A sleep number bed if well taken care of should last you at least 25 years since sleep number warranties the sleep number bed for 25 years.
Although the warranty only covers full repairs for the sleep number bed for the first 2 years and then you'll have to pay some of the repairs to the sleep number bed after the 2 years.
I'm not sure if a sleep number bed will last the full 25 years but even if it lasts 15 to 20 years that's pretty good for a bed.
I replace my bedroom set and mattresses long before the expected lifespan because I just sometimes want something new to update my bedroom and a new mattress and bed set helps me sleep better which improves my quality of life.