i am not sure about the plastic going away but i do know that if you leave the later ones with the elec fuel pump in it, the top of the pump, starts to go away along with the vent valve and what ever other plastic is on the pump assembly. i have a r/c tank and i went out to look at it and it seems fine. it is a 78 or 79 i think. it has been empty for years and stored inside garage.