I would never spend a full week (inc Fri and Sat) at VGC...but then I rarely pay weekend points at WDW either.
I think there is PLENTY to fill 5n/6d at the Grand Californian--especially if trips are limited to every 2-3 years. Those two parks have a LOT more attractions then any two parks at Walt Disney World. In many ways they have the best of the WDW attractions plus many of their own unique experiences (Indiana Jones, DL subs, Matterhorn, Space Mtn, Grizzly River Run, CA Screamin, etc.)
And you can't beat the intimate nature of the entire complex. Getting to DCA from the Grand Californian takes about as much time as walking down to the BoardWalk Bakery from BWV. Downtown Disney is the same distance thru another door. Now THAT is convenience!