The original Hess trucks are worth money and the later are not, pretty much the same way other collectibles went. Back in the day, nobody saved them, they were just toys for kids. Later on, everyone thought they were funding college from the profits of the trucks they were buying!
Hess headquarters is a tall building right on Route 1 in Woodbridge, NJ. So there were a lot of their stations around my home in NJ. Hess traditionally puts the trucks on sale at their gas stations the Friday after Thanksgiving. They usually park a tractor trailer or two full of trucks behind the station. Early that morning, there would be a line around the block to buy them. Of course that was once I was an adult and those trucks aren't worth much since they distributed so many and so many people kept them mint in the box, hoping for future profits.
My Uncle Dan bought us the originals when they were new. I'm 54 and I remember having the early Mack tanker with the working lights. Of course long gone. He died at 93 two years ago and I helped clean out his house. He was a car guy and a bit of a depression era hoarder so I found some interesting things in his house, especially in the basement. And the whole time I had my eye out for mint in the box Hess trucks! Never found any!