We did it a couple of years ago. Until the end of 2011, you could book either the Premium or Platinum Plans for just one night. If you checked in early on the first day (like 7 AM), you had that day and the next day (your "check out day") to enjoy the privileges of the plan. I read about it here on the DIS and my sister and I, along with our husbands, did an adults-only trip to do it. We had a room-only reservation on a Sunday night (arrival), "checked in" for our Premium Plan early Monday, and were able to use the plan entitlements until midnight Tuesday. We followed up with another one-night room-only reservation Tuesday night and left for home Wednesday morning. In the 40-ish hours we were on the Premium Plan, here's what we did:
-Had breakfast at the Pop food court OOP, got our mugs.
-Drove to Epcot and had early entry to do the 8:45 Segway tour.
-Finished tour, went to Le Cellier for lunch (1st credit).
-Spent afternoon doing Epcot attractions.
-Had dinner at Les Chefs de France for the Candlelight Processional (2nd credit).
-Went to 8:15 CP, then reserved viewing for Illuminations at 9:30.
-Shopped for souvenirs till 11:00 or so and were among the last out of the park.
-Went back to rooms to crash.
-Next morning, got up and had breakfast OOP at Pop.
-Went to MK for early arrival before park opening. Keys to the Kingdom tour 9:00.
-Lunch included in tour so no credits needed. Finished tour at 2:00.
-Spent afternoon at MK.
-Dinner at CRT, left just as
MVMCP was starting.
-Drove to DTD for La Nouba show.
-Went back to Pop and crashed.
Doing it for only one night we definitely got our money's worth out of it, with La Nouba, 2 tours and 3 expensive meals. (Signature meals and CP only use 1 Premium/Platinum credit, not 2.) It was a whirlwind, but we are all Disney veterans and really just wanted a chance to do the tours and such.
NOW, you have to have a 3-night minimum stay to get the Premium or Platinum Plans, so I'm sure it's a lot harder to get your money's worth.