What do you mean self insure?? You mean just pay for them out of pocket?
Yes, if he can afford to. The reason is because you can only contribute up $3,250/Single, $6,450/ Family to an HSA. Using that money for prescriptions eats away at the account balance and those funds can't be replaced. You want to contribute the Max, and grow a large balance while you're young and healthy and only use it when you have to (emergencies). Once the balance is up to a couple of years of Deductibles/Max out of Pocket, go ahead and use it for prescriptions.
Again, if paying prescriptions out of your pocket is too expensive, like $100 +/month, then use the HSA.