Tink, I don't remember having to wait that long, even for the princesses. The only exception to that was captain Jack Sparrow outside the theatre one night. (The wait was probably not as long as it seemed and it wouldn't have been so bad if there wasn't a pair of really bored and unruly little boys in line behind us buzzing and frequently colliding with everyone in the vicinity of their seemingly clueless parents. I digress.)
Of course, you could give the items they want signed to guest services. If you put the items in a bag with the name to whom it should be signed, the character whose autograph you want, room number and a sharpie, they'll take care of it. That might take all the fun out of it, though. Personally, our limited experience is that if you arrive 10 to 15 minutes early, it pays off. You're bound to see people holding places, and that's kind of frustrating unless it's someone holding your place.
but it's not like a few extra people are going to make the difference in whether you get a turn or not. I admit I've done it. DD was in the Club and couldn't be signed out because it was transition time (moving the kids from one part of the ship to another). I got in line for her and walkie-talkied my husband to bring her down as soon as he could sign her out.
Another thing, it's not uncommon to run into the characters on their way to or from an appearance, and they don't seem to mind being stopped. Our kids met Peter Pan, The Mad Hatter, Captain Hook, and Snow White that way. After the first encounter, when the mood struck them, they started carrying their autograph books around.
(Can you tell I have never mastered the virtue of patience? 
)
Now, better sense would say to wait until closer until we leave but for some reason they don't sell bathing suits in FL in the summer unless you go to an expensive specialty store. Go figure. 
