ALL of the resorts are getting a bit harder to get at the 7 month window. However, at 7 months, the availability is often BEST for SSR, OKW, Animal Kingdom and Poly.
Don't expect to just be able to book any full week that you want, at Poly at 7 months, especially during the Fall Food and Wine time. HOWEVER, if you actually start RIGHT AT 7 months and learn how to use the WAITLIST, you should be able to do it. I suggest you put in a couple of requests on it - splitting up your vacation block into a few days, rather than just a sold week - and then just piecing the days together as they come in.
Start with blocks of 2 or 3 days. I think your chances of getting what you want are excellent. If you own somewhere else, make a reservation BEFORE the 7 month window at your home resort. Split it into at least 2 blocks, say Thursday, Friday and Saturday (since those are most popular) and Sunday, Monday, Tuesday and Wednesday. Then, set your waitlist requests so that when one of those blocks is filled on your waitlist, it REPLACES the same block on your home resort. If you have LOTS of points, you could even just keep some duplicate reservations for a while at your home resort AND Poly, and then kill your old ones once the new ones are done.
Poly is a large resort with a lot of turnover in the reservations. SO, If you start using the waitlist very early and put in your waitlist requests starting right on the first days, at 7 months out, you should get good priority. The same can be said for Animal Kingdom - Kidani, which is an incredibly large resort with so many rooms that Waitlists are usually pretty easy. At Jambo and Kidani, the Jambo rooms generally go first, with the VALUE rooms being almost impossible to get (though I have got them, as an owner, through the waitlist). Next most popular are Standard Studios at either resort, and then other standard rooms. I personally love the Savannah View rooms and always choose them, but I understand that a lot of people want to save points by using Standard. At Poly I only use Standard View. I don't see the great thrill of looking out over the lake, since you can see it just by going to and from your room at other buildings. Or by taking the Ferry or the water taxi to Magic Kingdom.
Personally, I understand that people like the IDEA of POLY, but the actuality seems to be a bit less popular. That is why it is generally one of the last PREMIUM resorts to fill up. Personally, I don't see the attraction, except to do it just once or twice. I like Kona Cafe, and I like the ROOM Service for TWO from Ohana, but the Monorail isn't that big of an attraction to me. I find the rooms to be very generic, though nice enough. I don't think the grounds are especially attractive and I just like other resorts better.
I own 325 points at Poly and kind of wish they were somewhere else. I have 275 at Bay Lake and I like those And I have 400 at Animal Kingdom and I LOVE those. There is nothing wrong with Poly, per say (though I don't prefer it), but I like Animal Kingdom lodge much better. If I had my druthers, I would own at Boardwalk, I love boardwalk, too, but I'm NOT going to buy points that expire in 21 years when Animal Kingdom still has 35 years or so to run.
Anyway, I recommend you also take a look at Bay Lake Tower and Animal Kingdom. And I strongly recommend you consider buying on the Resale market instead of direct from Disney. the 325 points I own at Poly are Direct, and DIrect is nice, but not worth it. If you ask me.