There are still slowish times for DVC, but remember that DVC sold enough points at every resort for the resorts to be basically fully occupied year round. Which means by check in date - regardless of if its a slow early May or a busy early December - DVC resorts are booked pretty tight. The question is how fast they book.
By six and a half months, availability is spotty for most of October, November and December. But if you were booking a June trip six and a half months out - availability wouldn't be spotty until more like three or four months out (although those high demand low supply rooms are ALWAYS hard - sometimes even right at eleven months). By sixty days out, no matter what time of year there may be availability issues - although SSR and OKW will often have something, and people get lucky even right up to their travel date, especially if they snag a cancellation before it is allocated through the wait list.
If you want maximum flexibility, DVC is not a good choice. DVC offers a good combination of value with flexibility. In fact, if flexibility is what you are going for, RENTING points is the best possible deal. It isn't that much more expensive than owning points (far cheaper than getting reservations through CRO) and you simply find an owner who has the points you want. The second best possible choice is becoming a DVC land baron - and own points throughout the system. Both those will still involve being able to plan ahead.