Here is why a week charter is the bare minimum:
A. It takes me - and I'm not alone in this - 24 hrs to get my "sea legs" on board.
B. It takes me another day to get into the "island time" groove, where I'm not in any hurry to do anything...and the relaxed vibe kicks in.
C. The last days sailing in the BVIs are the best days of the week. You won't want it to end. Second trip down we chartered for an extra couple of days...and it still wasn't enough. Days 5/6/7/+ are superior to day 1 or 2. Charter for at least a week if you can...you won't regret it. You WILL regret NOT chartering at least a week though...
D. Lots of great info all over this board. Use the search function and you will find answers to your many questions. Folks on this board LOVE to talk about the BVIs because well, they LOVE the BVIs.