Awesome! Sounds like fun!

I do plenty of very long distance stuff :-)

Most of us would say that back to back riding is important. You don't really need to do a 150 mile ride in preparation for a 200 mile ride. I do think doing back to back 100's (sat/sun) work well in preparation.

Elevation change is a tough one--hill repeats, hard gear intervals on the trainer, drive somewhere to ride real hills one time.

Work on some of your deep-in nutrition. I like coffee/chocolate covered coffee beans, rice krispy treats, etc.

Feel free to ask anything else!