We extended a stay once for another two days - decided while we were already there. It was PHENOMENAL to give ourselves that freedom.
I leave the 5th, and am also hoping it re-opens a smidge early, but not counting on it, of course. DH tried to talk me into extending our stay one day (not for Philharmagic, just "because," - I couldn't get another night at POP or any of the other values on the plan we're on, though, so we haven't done it. I might call back a time or two and see if anything changes). If I could afford the extra night in the hotel, the extra day of tickets is nothing, and I'd say, well, if we can, why not. It wouldn't be ONE thing that kept me there another day, though, just the general joy of it all.
That's a long drive. I agree with the poster above that you should be well-rested before heading home.