I have this terrible habit of leaving clothes on my bed… lots of them, for weeks, months even. I would say maybe 15-20 lbs worth? I just wanted to know, from a technical perspective, whether or not that would have a significant enough negative impact on the mattress that I should worry about it. FWIW, my mattress is a gel memory foam type and has a 3-layer, progressive construction. I can provide additional specs, if need be, but I’m looking for more of a general consensus. Also, if 15-20 lbs wouldn’t do it, at what weight would it start to take its toll on the foam?
I don’t think that anyone could give you a specific weight partly because there wouldn’t be a specific cut off point where the effect would suddenly become a reason for concern and the effect would increase gradually as the weight increased and partly because it would depend on the density of the pile (clothes that are spread out over a larger surface area would compress the mattress less than clothes that are the same weight that are concentrated in a smaller surface area) but I don’t think that any reasonable amount of clothes that would still leave room to sleep on the mattress would be a reason for concern … at least in terms of the durability of the mattress.
I do not have experience with the static weight on a mattress, but I do have a La-Z-Boy recliner with a polyfoam cushion that has a permanent depression. The depression was caused by a stack of books, about 15 lbs., being left on it while it was in storage for a year.