What kind of hard hat do you prefer?

There's no actual "rule" most manufacturers recommend replacing them every five years from the date they are put into service, which is recommended to be written in the hard hat when its first put into service. The date stamped into the hat is the date of manufacture, we have hard hats in our supply cage that are a couple of years old and they still have their full life expectancy. As long as they're not stored in the sun or other caustic environment.

Here's the hard hat excerpt from the OSHA regs;

 

I have an MSA Skullguard phenolic full brim. Bought it off zoro.com for around $70 or so. Most other sites they were over $100.