We are scheduled for just 3 nights at Bay Lake Towers in January at the sale price of just $225/night for a lake view room. We go once a year or so, so this is about right for us. We have some airtran credits to use so the flight will even be cheap. Flying from ATL we can be down there by noon the day we arrive, and can leave later in the day on our departure day, so you get about 3 full days for parks. Staying so close to MK eliminates wasted time on buses and car rentals are dirt cheap this time of year, just $100 for 4 days including fees. So even less wasted time getting to the parks. Compared to a week in peak season, fighting crowds, waiting for buses and meals, standing in lines, you probably see/do nearly as much in 3 days this time of year (midweek, also).
Much more than than and I start to get a little homesick and eager to catch up on things at home anyway.