I've crashed going downhill in Scotland wearing a Giro E2, landed on head and left shoulder.
Cracked my collarbone (in 3 pieces actually) and the lid saved my skull.
Not wearing a helmet on the road is bonkers, there's no end of silly idi#ts out there driving tonnes of steel like there's no tomorrow but I am guilty of it too. Now I don't mean to lecture, but woul like to add some words of common sense (and applied engineering).
Helmets protect you by absorbing crash energy. This is a one way process, once energy is absorbed the capacity is gone. think of it as the crumple zone in your car. SoAfter a crash you ditch the lid, period. To promote good practice most manufacturers offer crash replacement schemes at reduced prices.
And secondly, The plastic in the helmets that does the absorbtion also loses capacity with time. This is not a marketing plot to sell more helmets, Long time ago I used to age plastics in a lab professionally. The solvent that is used in the production of the foam slowly disappears and the foam gets more brittle as a result, reducing the energy it takes to squash it. Without the actual data it is hard to put firm statements in but I ditch any lid after about 5 years, crash or no crash. And I never hand down my used old helmets to my loved ones, nor do I offer used helmets for sale.
Not sure that I have succeeded in not lecturing, but this stuff matters to me.
Enjoy, and be careful out there
PS somewhere in your helmet the manufacturing date is printed or embossed, have you checked it? At least you then know the risk you take.