Following the eating, drinking, pacing advice, you'll be fine.
Also, what's the most miles you've done in a week? General rule of thumb is that most people can do their typical weekly mileage in one day. So if you've had 100km weeks,it won't be a big stretch to do a 100km ride.
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You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.