“Your friend?”
“Yes. I shall tell you about him sometime, if the mood takes me. Still, our reunion banquet was quite replete. If only we had not been interrupted, we would have gone on for three days and three nights.”
That tremendous battle... for three whole days...
Gilgamesh’s words made Tine feel faint, and nervous sweat ran down her back. It was no joke; if the King of Heroes said so, then he really could fight for three days and three nights. If there was any reason he could not, it would be because she was his Master.

Fate/Strange Fake: Volume 2, Chapter 6 ("Day 1, Noon")