Well, I have not been to WDW as a
DVC member yet (just bought into DVC a couple of months ago). However, we were at the World in July and while I did a TON of planning, our actual trip was awesome because we did not wait in any long lines despite the fact that it was busy summer season. Not Christmas time busy, but busy nonetheless.
Here's what I did: I used Tour Guide Mike and it helped tremendously. Before that, I had made up daily itineraries for each park and saved them onto my computer. I was dead wrong with many things in my original itinerary according to TGM. I read and read many articles on his website and decided to listen to him (a common quote he says over and over again is "after all, that's what you're paying me for!"). I listened. I paid attention. I completely turned our original plans upside down and re-did everything according to TGM.
I am proud to say that the LONGEST line we waited on was when DH went to grab a FP for Exp. Everest at AK and texted me from there asking if I was okay with him just waiting the 30 min. wait and then if he would meet me to go to Festival of the Lion King. I said it was fine, because I was in DinoLand USA with the kids and we were enjoying ourselves there. By the time we had left to walk to get to Festival of the Lion King, it turned out that he had started walking as well from where he was, and we ended up arriving at the line at the exact same time. Couldn't have planned it more perfectly! So that wait was worth it especially since the kids were occupied.
By using TGM's advice (5 days at the parks and it worked every time), we were able to see all the attractions we had on our list before 2PM. Most of them we saw before lunch which was usually around 11:30, then we did some after lunch as well. Then we took an afternoon break which was so nice. We chose to go back to our room and relax and nap, or just watch TV (loved the DVC info on there!

), but others would choose to relax in the pool at their hotel. We then only returned to the park if we had a dinner ADR, which was twice (once at Epcot where we enjoyed strolling around the WS and once at MK where we just enjoyed walking around and viewing the shows by the castle). Other nights we had a dinner ADR at a resort restaurant.
So, I do know that we will be much more relaxed if we do not get to see an attraction on future trips than we would have on this past trip, had we missed something on our list. We did not know for sure we would be DVC members when we were on that trip. However we did know we wanted to go back every other year and stay longer.
DH and I decided while we were on that trip that if we really do get to live out our dream and go every other year we would stay 10 nights instead of 5, and still only go to parks 5 or maybe 6 days. The other days would be to relax, shop at DTD, enjoy the pool at the resort, etc. Ideally, going to a park every other day and resting a day in between to really enjoy our vacation. While I will continue to use TGM as a reference for planning, I am now "primed" for Disney parks and know much more what I am doing. And I will be able to relax at the World and take time to take it all in!!!