I think it really depends on your level of personal stamina. I have no problem going hard at a park all day, then partying at PI all night. I may sleep in a bit the next day...maybe not make it to the parks the next day until 10 or even 11. But the schedule I normally keep takes an immense amount of stamina, so I'm used to it. Most people I know can't keep up with me... so if you're the type that needs to rest and recharge, then I would plan for an easier day the day of, and maybe the day after, PI. As others have pointed out, there's no real point in getting to PI when it first opens, so you have plenty of time for a rest between things if you need it.