Note to self: Don't ask about what other like minded people do. Just lurk on the forums and wait for them to volunteer the info.
I'm sure that you aren't trying to come across in a negative way. But this is the internet. Similar to text messages or email, the only tone or intent that is perceived by the reader comes from the reader. So it is real easy for folks to read some of your comments like this and those on the "poll" thread and conclude that you have an attitude. And generally speaking, being new to a group such as this and having what is perceived as an attitude doesn't make a lot of folks want to open up and share/help/answer questions. I debated on replying with this because I try to follow the basic rule that I should assume those who read my comments will do so in the worse possible way and if my comment/post could be taken in a bad way, I edit or delete. So don't take this as an attempt to start any type of disagreement, we are all here because we enjoy riding long distances and gathering with like minded individuals.
To answer your question, it depends. If I am riding for a goal such as a rally or a ride that has very little room for error or making changes on the fly, yes I plan it out in detail. Examples:
I am planning an in-state EggSanity Gold for Easter weekend. That ride will require that I visit all 4 chains, while riding over 1000 miles, all without leaving the state. Doesn't seem difficult and I can do a minimal amount of planning for this ride. Just pick a route that hits the mileage and 4 egg dish minimums while staying inside the state. So I'll pick my 4 locations and verify that they are still open (took 4 Huddle House tries last time to find one still in operation and open after 10pm last time), then add a few shaping/turn around points to be sure I'll hit my mileage and play the fuel and other little stops by ear. So this one gets a moderate amount of planning.
I rode a SantaSore 1000 on 12/25-12/26. With that ride, knowing I just needed the miles on a certain day, I simply worked out a quick 1000+ mile route. I knew I had time to find gas/food and take breaks along the way and I had plenty of freedom to ride as I wanted.
I am considering a BBG on Leap Day. This ride will take a great deal more precision than the others. I have to complete at least 50% of miles and hours on 2/29. So I can't leave out before noon on 2/28. I also have to be at work the evening of 2/29 at 6pm so I don't really have time to stretch the ride out very far into BB1500 Silver territory. So, I will plan fuel stops, based on Garmin maps (basecamp) and google maps/street view so I know what side of the road they are on and I'll check for road construction on my planned route. I will plan it as close to down to the minute as possible. And I will set time/location markers along the route to make sure I am on time and know if I need to abandon the BBG and convert to a SS1k.
So I suppose to answer your question, the ride determines how in depth my planning is. I'm sure those with multiple BBG's under their belt can hop on the bike and ride one with almost zero planning, silimar to how I can ride a SS1k. So plan your ride until you are comfortable that you can acheive your goal with your plan and then ride the plan.