I can not speak from experience because we have not done a split stay, yet. But I hope to in 2017 (next year's vacations are booked solid). We have only done one WDW vacation where we stayed on-site for more than four nights; that was at WL for six nights. The rest have been as little as one and as many as four, leading up to a
DCL cruise. When we do a split stay it will be a minimum of six or seven nights, using one full day to skip the parks, transfer from one resort to the other, hit DTD, miniature golf, etc.
We actually make the resort just as much of our destination as we do the parks, going back in the middle of the day to rest a little, make dinning reservations, horse carriage ride, water mice rides, explore new territory, what ever is offered at the resort we are at. If I were to have only two nights at the resort it would only be if we have already stayed there before and know it frontwards and back (or leading up to another DCL cruise).
And I knew we had at least four more nights at the resort we are moving to. One of our goals is to stay at as many WDW resorts as we can; while we still can, not that I'm getting up there in age
And this is the reason I want to do a split stay next time, to stay at resorts we have not been to before.