I'm not sure you'd need a full 90 minutes or more to stake out a good spot. We were there on 3/11 (a CL7 day, per TouringPlans), and we didn't grab a spot until 30 minutes before the show. We ended up about three rows of people back and just to the left of center in front of the stage where they do the SW character show during the day. We had a great view of the projections, a perfect angle for the fireworks, and the other effects felt like they were all around us. Of course, YMMV, but even in the summer season you should be able to find something doable without sitting there for 90+ minutes (IMO).