I've never heard of Purple. I have a Simmons, I believe, that a relative purchased for me not more than a few years ago. It's holding up fairly well, but starting to sag a little around the edges, and where I use my elbow to prop myself up, the foam-topper inside the mattress, has started to break up, so I can feel the coils. My fear is, that 3-4 years in, the coils will start to expose themselves to my elbow.
Part of my problem is, I weigh... well... a lot. I can still get in and out of bed, but I huff and puff sometimes, moving around from room to room.