Alot depends on the course, sea conditions and how fast you cruise. Four or Five days sounds like too long, but if your going to hang out at places then I can see that. By course you have a choice on the South Shore of inside or outside. Personally, having done both, I enjoy the inside alot more, there is just alot more to see and look at. Cruising in the ocean is not bad if the ocean is calm, but it is very boring! Inside you see nice houses, boats, etc. If you plan to go around Montauk and not take the canal, then you would have to outside, at least at shinnecock inlet. East River is also not the most pleasant boating with all the tugs, but its tolerable.