Vast fits somewhat, but as big as that might be it is not really unlimited.
Plenary fits a little better but it is pretty uncommon.
I like amaranthine. How many times do you get to use that?
Also:
plenary, everlasting, all-inclusive, all-encompassing, comprehensive, forever, astronomical, vast, immense, enormous, extensive, bountiful, prodigious, titanic, colossal, absolute
If you avoid using epic, I will avoid throwing stones at you.
At this point, I'm so sensitized that I would prefer that people avoid using that word even where it's appropriate, such as in describing Beowolf.
 infinite?