Rich? Hardly, I finished school last May and have only been working since October. I just ride a lot more than most folks, though certainly not as much as some. I think I've covered about 120k miles (street) and have ridden off road since I was 11 years old. In that time I've owned about a score of bikes so I don't come at this as a noob.
The 5yr thing isn't old (for that matter neither am I - 25yrs ago I was in diapers) and I doubt its a gimmick. In any event, I'm sure that after being exposed to all sorts of weather and pulled on and off thousands of times my lids are pretty well trashed before 5yrs are up anyway - they certainly tend to look a bit worse for the wear. I'm sure you could go a lot more than 5yrs if you take good care of your lid, store it properly and don't ride a lot. Ride every day of the year in the north east or mid Atlantic and things take a beating. Without really solid empirical testing I'm not risking my head over what amounts to about $100 a year. If you wanna take the risk its your choice, but do it knowingly, not by making deluding yourself into thinking there's no risk.
My dirt lids rarely make it 5yrs as I crash too much.
If you are looking for a lid I really like the new Bell Stars - ultra light, cool and comfy. If you aren't picky about the paintjob you can find them for less than half of retail.
You wanna buy some old (non-crashed) helmets?
I've still got an Arai or two laying around that I didn't wear more than once or twice...