With that break, it sounds like you are basically going on two 30ish mile rides in the same day.
My general suggestion for anyone based on my limited experience may apply for you (especially on the second half), and that is to be sure to pace yourself, and don't ride fast based on the excitement of going on a great ride. If you start out a little slow, you will enjoy the end of the ride a lot more.
If you haven't spent much time on the bike recently, follow the above suggestions on food/water, take your time, and you will only have one more issue... your body not being used to spending 3+ hours in the saddle in one day. Be sure to stand occasionally, and wear some good shorts that won't chafe.
And also, at this point, you can not get your body in any better shape at the last minute for the endurance, but do take some nice easy spins between now and then.
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Slow Ride Cyclists of NEPA
People do not seem to realize that their opinion of the world is also a confession of character.
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