That "unlimited redemption" feature for Hilton was for a limited time only, starting January 2017. (That's been noted before on this thread.)

Before that, it was once every 90 days. So 60 days is actually an improvement over the "normal" situation for Hilton redemption. (Most, perhaps all, e-rewards redemptions have limits of this sort.)

Also, as I've posted before, these conditions can actually vary from one user to another. Specific example: some gift cards are redeemable once every calendar quarter for one user, but the same ones are only once every 180 days for another user.