4-5 nights will be enough to spend in Karrajini. You'll do all the major gorge walks in 3 days. Another option to consider is to head up to Coober Pedy and come across the Anne Beadell. The Anne Beadell was graded last year in the roughest sections around Emu airfield, so it should be a reasonable run and if in a hurry, 3 nights will cover the AB. I'll be heading over the AB enroute to Fraser Island etc in late August. I think the drive through the Great Victoria desert section and the red dunes is simply awesome country.