"And your mattress doubles in weight every eight years"

I'd never heard that one before.

https://www.snopes.com/fact-check/mattresses-double-weight-e...

As the plasticizer leaves plastics, it becomes embrittled.

You want the EPS to crush smoothly -- if it cracks and displaces, it will not be in place to absorb energy and cushion the impact further.

We replace our bike helmets every ~6 yr.

Source: Have listened to the crackle of decade-old plastic kayaking helmets under tensile/compressive stress and watched them shatter like glass after impact with a concrete floor. New helmets from the same manufacturer did neither.

> That is just a way to sell more product by shaming people into "being safe".

The cynic part of me agrees, but is it though?

Some plastics seem to get "stressed" over time, especially if under sunlight (not sure if it's the temperature or UV that's the issue) - I wonder if that's part of the concern here?

Guy in a motorbike shop told me it's UV that makes styrofoam lose its useful properties, a quick Google seemed to confirm that.

The guy in the shop wants to move helmets. The internet is littered with factoids that "everybody knows". It's on the internet you know.

I've never seen any motorcycle helmet with exposed styrofoam though.