9. While largely heralded as the antithesis for inflation - deflation (block halving down to nothing) results in early adoption getting wealthy by the magnitude of adoption. At the expense of the wealth being represented by more coins / inflation. This directly discourages future adopters as the wealth goes towards the early people rather than spreading to more units.
4 years between halvings is actually a lot of time, so I think it is fair. Much larger impact is the number of people mining, but you can not have both - high adoption and everyone mining full Bitcoins...