Having ONE helmet is like having One pair of underwear!
IF you are serious about riding, then I think that the average rider, riding 7days a week or so, should have a minimum of two helmets. I have several that I switch out. On hot days I get really sweaty inside and it doesn't hutr to wash and wear, but I prefer to clean it and then let it air out. I have a clean air filter system in my room, it uses very fine HEPA filters to keep pollen, molds, cat dander...dust...anyway, that I set freshly cleaned helmets on or next to. I like to switch because somedays I'm just going into town and back and sometimes I'll be on the road for longer periods of time...always nice to have a selection. When you start cycleing helmets you can really find one that you want for the longer road trips...it not only feels right but is quiet, and easy to clean and such...starting out with 4 helmets would be quite expensive. I'm retiring two of mine pretty quick, and when I do, I drill them and tear out everything so that some fool doesn't try wearing it after it's life is gone out of it. I also change my Military lace up boots for the same reason. I have two pair that I wear, and one pair that I always keep super clean and for Inspection. Actually I do wear them from time to time in the house to keep them loose, but I never wear them outside anymore. (Read Retired Navy...and always have a Uniform ready for inspection...old habits seem to never die, just people.) I say, when you can afford a second helmet do it; when you can afford another do it and rotate your helmets.. Having one helmet is like having one pair of underwear....