Making Anakin 9 in TPM was also a huge mistake. Not just because the character was too young to be effective, but because his future love interest was almost 5 years older. I don't know many 24 year old Senators who'd fall for a bratty, whiney 20 year old boy (he must have been almost 10 in TPM, and Padme just turned 14). As for a planet 'electing' a 14 year old girl as queen...
Also, how long did Luke spend on Degobah? The film makes it seem like days, but surely he couldn't have become that good in such a short space of time. I've also often wondered how long it took the Falcon to get from Anoat to Bespin on sub-light drive. Then again, these are only films, and perhaps I think too much. Still, it would be nice if Lucas could at least attempt a bit of continuity. On that note, why the hell did it take 20 odd years to build the first Death Star, and less than 5 to build the bigger, more powerful second?