There is rarely any incentive to preorder a game early.
I'll typically preorder a physical game a day or two before it comes out if it will get me any additional content. Plus, with physical I always have the easy option of canceling to get my money back. But putting money down long before the game comes out theoretically cost you more if you are making any interest off your money. It's a negligible amount, but still, the company you are giving it to is trying to do the same thing, and turn your money into more money.
With digital, especially from Sony, I don't think there's ever been a reason to preorder well in advance either. The same theory holds true for the financial side of things, plus there isn't the freedom of a cancellation policy should you not want the game for any reason. In the cases where the have a preorder discount, I'll just wait until right before release to make sure I can't get a deal elsewhere.
It boggles my mind when I see huge, unproven AAA games - especially new IPs - asking for $60 on PSN months prior to their release, at point when they're not much more than a trailer. I really hope no one is crazy enough to be blindly preordering that stuff.