If you're like me, there are times when you prefer a firmer mattress and there are times when a softer mattress would suit you just fine.  By purchasing a Select Comfort Sleep Number mattress I can change the firmness anytime I'd like!   My uncle bought a firm conventional mattress and found that, although it felt perfectly fine in the store, sleeping on it was a whole other story.  I recommended the Select Comfort Sleep Number mattress to him and he has been a happy 85 ever since!  It's the best investment we've ever made.