When I began to plan for my thru-hike of the Arizona Trail, I didn't spend much time thinking about what I’d do after I got south of the Grand Canyon. I only thought about the first week, and I did that on purpose.
There's not much to gain by working out many details of a thru-hike in advance. I've known this for a long time. When I tried to ignore that wisdom during my Appalachian High Route thru-hike, it didn't work. I had to revise my plan several times.
The only planning that really matters is figuring out how you’ll get to the trail and how much food you’ll need for getting to the first resupply stop. From there, you just need to think about getting to the next resupply stop. That’s what I did for this hike.