If you can handle that easily enough you sound like you should be fine.
I was knackered after Sunday's ride, and found that on the ride I did today (54ks) I tired more quickly.
As yet I would struggle to do 80ks in one day. If I stick with my current training however I should be ready come November.
Hoping to achieve at least 100k ride before then.
One good tip from the ride on Sunday - for meal times take a bag with you that you can put things like the bread roll, pieces of fruit, muffins etc into as you collect your meal - otherwise you can run out of hands.