Originally Posted by Anglo Large Clawed Otter

About 3 full days would probably be good. If that were the case, I'd see about building in side-trips to other places, like Iguacu (one day with overnight, max), and EZE/MVD/MDZ. If using 2x One-Way tickets on BD miles, you can haz two stopovers. :-:

ETA - You might have to book a relatively cheap one-way ticket to make it all fit together, but there can be some surprisingly reasonable one-way fares in S. America.