Don't know if anyone has tried it with one as old as mine, but there was a test long ago of a well-used (and yellowed from sun exposure) Bell Biker that was about 15 years old. It passed the tests without any problem and performed the same as that model did when originally tested for certification. I have no reason to suspect that mine would do any worse. Polystyrene foams and the Lexan of the shell are both very stable materials.

I do also have a newer helmet (for the lighter weight), but I'd actually trust the protection of the old Biker somewhat more - not that I think any regular bicycle helmet offers much protection.