Hi James.
David has given you the headlines. I would add you do need to plan ahead if you have very specific date/ location requirements. We are staying at the Grand Californian Villas and I needed to book at exactly 8am EST 7 months out to secure my reservation. Literally seconds later the rooms were fully booked. Admittedly this is probably because Galaxy’s Edge is opening, although from reading various reports, GCV are often hard to get. It is easier to secure rooms at Walt Disney World, although there are some dates which book quickly such as Thanksgiving, and whilst rooms are likely to be available, maybe not the size of room or location you may have preferred will be available.
There are dedicated DVC sections on
http://www.wdwinfo.com which I would recommend as they include details I wish I had known before we bought such as home resort booking priority and cost of annual dues, as dues do vary by resort.
I would also add, whilst a key selling point is using the points outside of Disney, we never have as the ‘value’ is less good, although I appreciate this is a personal view. We have used them to cruise with Disney though. Many say you need to buy points where you want to stay and want to visit Disney a lot!
Happy deciding.
David