Helmets certainly have a finite life span. And if you smack your head into a tree hard enough to have a twenty-four hour headache as I did last winter while fatbiking, I highly recommend that you discard that helmet and get a new one. The tree incident happened in early March and I've been searching for a replacement and finally decided on this Smith Forefront 2 in matte gravy.
It's a bit spendy but as the saying goes, "if you have a $10 head, wear a $10 helmet". In this case, my first impressions are that you get what you pay for. It's possibly the best fitting helmet I've ever put on my head. It's goggle friendly and has a built in mount for light or camera. It's MIPS rated and has a cool looking honeycomb core but hopefully I'll never put those features to the test!