You can use the ROTH conversion latter with an HSA as well where you convert a portion of the money into a ROTH where it will continue to grow tax free and because it was a contribution, you can pull that money out tax free later on.

All the saving of receipts does is if you are in a pinch of some kind and want to reimburse yourself. The smart thing to do is save the money, invest it, and never have to touch it until retirement but life happens and you may find yourself in a pinch and you don't want to take a 401k loan or tap into other retirement accounts.