I'd consider this several ways.
160 charts and all day (inside or outside) is a whole lotta music. What is your price ordinarily for a 'regular' four or five hour job, and how many charts is inside that time frame. I'm thinking 160 charts has got to be at least the same thing as two nightly gigs' worth, if not three or even four. And are these songs you'll have to work up?
The other Gorilla in the Room, however: IS this being requested by your regular, long-term casino bookers, and would refusing this upset any of those relationships? If this would significantly alter or even derail those relationships and jeapordize your long term work prospects in these venues, it just may be one of those things you'll have to suck up and get through in order to keep long-term work. And if you do it, does this help those relationships by doing a tough one ?
These are things I don't know, but would be the way I'd be framing this in my mind, if you can re-negotiate somewhat.
Good Luck.