We always recommend 5 days (the most possible for a multi-day ticket) for the most relaxed trip. 5 days allows for rides, re-rides, shows, parades, dining packages, character meals, shopping, beach days, pool time, sightseeing outside of the parks, etc. Depending on when you visit, the extra time also allows for any events that are going on in the parks, e.g. Food and Wine, holiday events, Halloween parties, etc. And if the parks are very crowded, the extra time still allows you to relax and see everything you want. Park hoppers are great, but if you have 5 days, you could still do one park tickets with MP and be fine. Agree with the pp that 3 days would be the minimum with park hoppers and MP.