Wolfstar, GEM and snugs all told me that captions are really only needed to identitfy the others in the photos with POTUS, but I just cut and paste the captions as I snag each photo. After I have them all, then I decide which ones to keep or to post. It seems mundane to post "President waves as he boards Marine One for..." but I post it anyway...lol.
The captions I really needed were the ones of the First Lady and Condi.
I do the same or I edit the sentance it sometimes helps to know what to put. I have also noticed on several photos you will have different captions though in essence it is the same thing. I usually then pick the best description. I just find it helps to use the captions as a guideline but sometimes they are wrong so you have to watch it as sometimes they identify events or people incorrectly though they normally quickly issue a correction.