Exchanging and DVC direct are two whole different ball games. While, yes, you can possibly get last minute dates / trips, just don't count on it consistently. If you truly are flexible, and will go if you get the reservation, but don't need to go if you didn't get it, I have good luck using the DVC waitlist options for 1-3 days and getting the exact dates I wanted (Usually with 2 months since DVC points goes into hold if cancelled under 31 days). Any longer trip and it's difficult to get that reservation date, even on a waitlist. If you have to to have a certain date, than you really need to book at 11 months out at your home resort. I mainly only gotten SSR or OKW at under 7 months mark (what you normally get thru II exchange anyways). It's hard to find anything for 7 days consecutively at other resorts under 7 months. Sure, I can usually piece a 7 days trip here and there with split stays across the various resorts (and with using waitlist), but it's can be stressful when you already book plane tickets but missing a day or two within your plan trip and still waiting on a waitlist request to come thru.
So as others said, you need to be able to plan with 7-11 months window if you are going to buy DVC points. Else, truly the math doesn't work out comparing to Exchanging thru II, if you are just going to wait until under 7 months anyways before planning and booking.
Great3