I went with my girlfriend at the end of November for 5 days. This seemed to be the perfect amount of time to go for, any longer and I think our legs may have fallen off from the amount of walking. It was also the perfect amount of time to see all the main sites (get some sort of pass that allows you access to the main ones, saves money). As long as your not a slow one and keep up with the pace of new yorkers then you will get to do and see a lot. Definitely recommend Juniors cheesecake too, little restaurant just off of times square, best cheesecake ever!