With some exceptions, booking your home resort before the 7 month window opens is not an issue. "Hard to Book" is mostly a discussion for the 7 month window and the smaller WDW DVC resorts (VWL, BCV, BWV). Booking the VB & HHI resorts is a separate discussion. AKV is still too new (and not finished) to have much history.
There is almost always availability at 7 months for SSR & OKW. Those are the largest WDW DVC resorts. The only real exception to that are the Grand Villas, especially those at OKW which cost less points than those anywhere else. Getting a GV at 7 months is difficult most times of the year.
In general:
VWL are more difficult beginning the week of Thanksgiving through the week that contains New Year's Day.
BCV and BWV are more difficult beginning in October (Food & Wine Festival at EPCOT) through mid-January (after marathon weekend).
Standard view and guaranteed Boardwalk view units are especially difficult during the above times and difficult all times of the year.
Concierge units at AKV are virtually impossible. They are almost always booked with waitlists long before the 7 month window opens. (There are only 5 2-bedroom lock off units in this category. So depending on how they are rented, the number of concierge units ranges from 5 - 10).
At the BCV, the 2 bedroom units with two queen beds in the second bedroom (as opposed to 1 queen and a sleep sofa) are difficult all times of the year, and especially difficult during the months listed above.
In general, January through mid-February, May & September are the easier months to book if you are using the 7 month window. Grand Villas anywhere seem to book very fast. Studios and 2 bedroom units book faster than 1 bedroom units.
Difficult does not mean impossible. But it does mean that you'd better not waste any time. When the 7 month window opens, many members will call day by day right at 9 Eastern (when MS opens) to book units at the smaller DVC resorts. Many will have to waitlist for what they want.
Some specific unit types have little to no availability at 7 months and are
virtually impossible to get at 7 months for some times of the year. Members who own at those resorts call day by day to get them and there are usually waitlists established for them long before the 7 month window opens. Examples of those include standard view and Boardwalk view units at the BWV during early December and concierge units (all sizes) at the AKL(all times of the year). There just aren't many of those types to begin with and you need to own at the resort to have any assurance of getting one.
FWIW, I expect the Savanna view units at the AKV to fall somewhere between OKW & BWV in "7 month difficulty" . I think the value and standard view units (which cost less in points) will be difficult to get at 7 months.
There are exceptions to everything, but the above is pretty much the way it has been the last few years. Again, this applies only to the WDW DVC resorts. VB & HHI have their own versions of the above.
P.S. I think booking the smaller resorts at 7 months is more difficult now than it has been in the past. IMHO, this is due both to the growth of DVC and to the developer points incentive. Prior to the incentive, I don't think Disney was able to rent all of the developer points via CRO and so DVC rooms sat empty. Now that those points are in the hands of actual members, they are getting "used to the max" and creating more competition for space at 7 months.