Scott, I used to have those plastic hang on cage cups and would put an extra 2 or 3 in the cage....I was always concerned bout having enough water.I think I said this earlier in this thread but in over 42 years, I have never had to rescue either of my birds while in the cage. My previous OWA never traveled with us so she was left home from 3-5 days at a time with no ill effects. I figure that she would stuff herself with the overabundance of food that I would leave and then just lounge around watching TV. Nike has been left alone once for 3 days, again no ill effects but since then we discovered that she is a good traveler so she goes with us now.
I would personally leave Parker for this long if I weren’t so worried about water bowl condition. I can minimize ability to dirty the water but not fully. I’ve seen what happens to his bowl after a couple days of not cleaning (minimal cage use during the day). The thought of high usage over several days terrifies me.