Take a look at this advert.
Ok, let’s think about this claim for a few minutes. The ad says that your mattress weight essentially doubles every few years due to the amount of dead skin, sweat and dust mites. I’ve seen it touted in ads, occasionally mentioned on (usually local), news like it’s proven fact and had it told to me by a friend last year when we were both mattress shopping. Is this true?
Well, let’s consider. I went to Ikea’s website and looked up your basic spring mattress. It’s the Sultan Harestua, and it weighs 30 pounds. Now I’m not sure how much sweat and dead skin you personally slough off, but in my case I’m pretty sure it’s not 30 pounds worth (and most of the sweat would evaporate fairly quickly anyhow). Even over the course of eight years I strongly doubt that I’m leaving behind that much dead skin and sweat, and as for dust mites? Yeah, I doubt that even a fairly massive population would contribute that much to my mattress weight, and any population that is large enough would likely be big enough to see.
So these claims (which, tellingly, are from mattress companies and less frequently from pest control companies), never made much sense to me. I did some poking around on the internet and found out from Cecil Adams that, yes, these claims are quite bogus.
I guess the message here is to consider the source. If a mattress company is trying to sell you on the idea of a new mattress, they have every interest in making you think you need to replace your old one every X years. But you don’t, really, unless it’s not comfortable to sleep on anymore. That’s the only excuse you need to replace it and really, it’s the best excuse there could be.