Yeah, the lad is a 2d10 purist, doubt I could even tempt him to a d100. In fact, I think he mainly wants a set of his own because I've loaned him a pile of non-standard dice I got in a Kickstarter (d6s in the shape of fireballs, d8s as potion bottles, even a d20 as the brim of a wizards hat, and most entertainingly d2s as spellbooks (i.e. Coins)) and I think it's driving him mad.
He's an insatiable tinkerer though, 5 sessions into running his first campaign (DnD 5e) and he has a list of homebrew "improvements" that he wants to introduce. I irritate him greatly by saying "yeah, you've just invented Runequest combat there", or "interestingly, that's exactly how initiative works in Hackmaster 5th ed". I view my insufferable know-it-all behaviour as a necessary broadening of his horizons, no DM is an island.