I've never transited through EZE, but I've passed by two waiting areas for transiting passengers many times. There are at least two, 1 in the newer terminal and another in the old building, both are hideous. Terrible seats, no refreshments, no restaurant or kiosk access. 8 or 9 hours would be miserable. You should talk to your airline and/or travel agent to find out what options they are aware of.