Yes, they're very restrictive. If you do manage to find award availability, it'll often be just for one night. The strategy I employed earlier this year is described in this post (#54) but it's basically: search for "flexible dates" and choose 1 night. Repeat every day. Book one night at a time until you have the stay length you want (and let the hotel manage the "merge" of the nights when you check in). At the time of writing this, I can see a night in January and a night in February (which matches what I saw back in June when I wrote about the strategy so I guess it's still viable).

edit: I should add, I like this hotel a lot (my review is earlier in the thread) but if you want to really enjoy it then you're going to need to spend a lot of money. The room cost is only about half of the cost of staying here if you want to eat and enjoy the facilities and services. So, even if you can get a room on points, be prepared to spend $500 USD+ per night.