When we used to go every two years or so we would plan, plan, plan, plan...
A couple of years ago after micro managing many trips..I said the heck with it..detailed plans are out the window now for us two.
Now we plan what park to start the day in and maybe a few PS but this coming trip we are not even making the PS as we are not sure what we are doing and going. In September we have just walked up to restaurants just fine in the past, so we are going with the flow.
Last year we ended up even modifying our what park each day do we start in plan due to cold weather and rain..the Epcot is a better rain park theory we call it...
So if you take very infrequent trips or maybe once in a lifetime I say plan away and make sure you do see the things you want to see this trip. But for those of us lucky enough to go fairly often,at least once a year, i saw go with the flow. Have a rough idea in your head, but be open to last minute changes and decisions to do other things.
I was behind a family last year on Maelstorm in line where the Mother was kinda belittling the Grandmother who was along for ruining the "plan". She was saying to the kids while the Grandma was still there, well Grandma ruined our PS to have dinner at Akerhaus at 4pm, since she insisted we have lunch at Biergarten at 1pm today...
BE FLEXIBLE, BE FLEXIBLE, BEFLEXIBLE IS MY MOTTO