My 64 miles was done on a bowl of porridge and a couple of bananas (they needed eating and I don't like to throw them out). That was not fast and mostly flat. I didn't feel any kind of bad/tired, but then it was a leisurely 15mph bimble. A bit faster on the return leg than outward, but still nothing really strenuous, for me.
Previous ride of 35miles had hills in it, and I felt sooo bad.
Maybe I'm just not cut out for hills, they seem to sap my energy instantly and that feeling lasts... i.e. generally hills don't get any easier, or maybe I'm just trying to go faster than I can keep up (18-20 on flat(ish) and however fast I can get up hills)
Next big ride will be over in cumbria at the weekend and I'm sure that place has hills in it
I'm just gonna take some peanut butter/jam sammiches with me and have a decent breakfast. I'll be going with gf's dad who's 64 and fit, and her sister who's recently done an ironman so I know she's good for the miles.
I expect I shall die.