I think it depends on your touring style in the parks. Are you rope drop to closing warriors? Do you want to do everything (!), e.g. rides, shows, character meals, all the rides multiple times for your favorites, M&Gs, shopping, higher end TS, dining packages for shows, etc.? Or do you like a more relaxed, go with the flow, type of park day? Will you be taking a tour, e.g. the Walk in Walt's Footsteps tour (has great history of Walt's original park!)? Depending on your answers to the above questions, I would say that 3 days is the minimum (get the park hoppers -- hopping is sooooo easy at DLR and totally worth the cost -- and MP makes hopping an advantage) and more days are even better. This also depends on the time of year for your trip -- when are you planning to visit? SWGE will open, most probably by end of May or by mid June of next year -- this is a major game changer regarding crowds. Other crowded times, like Spring Break or major holidays, also require more days for a less stressful trip. Will you be staying on site or off? On site gives you one hour early entry to each park on alternating days. This perk can help you get a lot done since mornings are key lower crowd times at DLR. On the other hand, staying on site isn't the necessity at DLR that it is at WDW. Some of the off site hotels across the street from the parks are closer to the gates than some of the on site hotels!
These links will give you lots of good information for your trip planning. Start with these, then come back with more questions!
A DLR Guide for WDW Vets -- read this for a good overview of the similarities and differences between DLR and WDW so you can have a better idea of what to expect and how to plan.
www.disboards.com/threads/choosing-the-right-hotel-for-you.3656512/ -- choosing a hotel at DLR is totally different from doing the same at WDW. This thread has great info.
HydroGuy Tips Compilation -- so many good links for helpful planning info contained here!