I'm sure this has been asked zillions of times, (and sorry of it has) but...
if you buy the two day parkhopper ticket
(a) do they have blackout dates?
(b) do you have to use them on consecutive days...or can they be used within a time period?
(c) can one "hop" back and forwards between Disneyland and DCA during the day as many times as you like?
I think that's everything. I'm sure someone out there can help me.