First, let me say that I am a HUGE fan of both TGM and the Unofficial Guide. But on this trip (14 days ending today), a different conventional wisdom worked better than either of the strategies laid out by either.
The touring plan that worked best was to arrive at the parks around 5pm, grab one set of fastpasses, eat a nice sit-down dinner, and stay until closing. Of course, use fastpasses whenever possible. But the number one strategy was to be ready to maximize the final 90 minutes of each park's operating hours. In addition, summer WDW visitors should feel free to attend the Extra Magic Hours nights, but it will be better if you can stay all the way until the end. This is a HUGE change from the past.
My daughter and I are theme park junkies. We routinely arrive at park opening. That strategy DID NOT WORK on this trip. Animal Kingdom really didn't work. Expedition Everest was an IMMEDIATE 55 minute wait (as was Kilimanjaro Safaris). It tamed down much later in the afternoon.
On EACH night, we were able to go on the most popular rides MULTIPLE times. Both Splash Mountain and Big Thunder Mountain were walk-ons during the final 35+ minutes. Buzz had NO wait the last 50 minutes. Fastpasses were available for Space Mountain until very late in the day.
My recommendation: Be flexible. It is VERY helpful to read both TGM and the Unofficial Guide, but you need to test your own theories as well. For us, this is the FIRST trip (in over 30+ trips) that we have spend the final week sleeping in, swimming all afternoon, and going to the parks until closing. It was different, but it was GREAT!