Stickers with solvent-based adhesives can adversely affect the plastic in your helmet, shortening its life.

That’s the line you get with hard hats and motorcycle helmets at least. To me, I think stickers make it easier to miss signs of damage. I don’t slap them on my helmets of any sort and I replace my helmets after noticing any signs of damage.

Stickers go on my water bottles and most of them are John Carpenter movie references.