If those 5% were the question of whether to go with the group on a adventure together or not - and you end up alone at 55 years and not invited .. you might have rather invested different back then. But on the other hand I don't think those 5% of earnings with 17 make a difference later.
The only real difference they can make, if they made you start a habit of saving income for important purchases. (But not really fore retirement at that age. But each to his own)