Replace helmet how often?

Shoei recommend replacing after 7 years from manufacture date and 5 years of wearing, I start looking around for a new helmet after the 5 years of wearing but don't stress about it believing if stored and cleaned correctly Shoei foam doesn't turn to dust after 5 years and 1 day of use.

Plexus is just for the outside shell and visor to help protect from the elements, bug guts and keep shiny.