I don't know how anyone can make it to 5 years on the same helmet. After wearing, cleaning, more wearing and such, mine ususally smell so bad after 3 years that my wife is begging me to get a new one. Mind you, I don't have a sense of smell, so I can't tell you how bad they really are.
Point is, I usually put 65,000 - 75,000 Km on a helmet in 3 years. They get jostled in the shop, in my top box, carried up and down hotel stairways, left in a locker and once or twice been accidently knocked into a ditch. They also get worn in sun, rain, sleet, fog and the occasional snow squall. I would consider myself GENTLY on my lid. But after about 3 years, it looks like its been through the Boer War and is ready for retirement. That's when I start looking.
The other thing, I've never bought a $500+ helmet. I do get one that is ECE and DOT rated, Snell if I can. What's the big difference between my $300 Snell Lid and your $500+ Snell lid?