Did anyone have a chance to read the articles in the original post? I believe the first one concluded that over a period of 24 years the helmets did not degrade significantly. Wipeout 1000 does make a good point about polycarbonate which degrades under UV with pronounced discoloration. As we all know ChatGPT is only as good as the info it is fed from the internet. https://www.sciencedirect.com/science/article/pii/S2238785421003793
