Syncing Genius Data taking forever

I have an iPad 3, an iphone 4s, and and iPhone 3GS (deactivatd and used strictly as an iPod. In experimenting with these I have been unable to determine any rhyme or reason to the Genius data sync bewteen my master library on my Mac and these devices. For example, I will do a sync with my iPad, make no changes but listen to a couple of podcasts and songs and then resync the next day and find myself waiting for Genius data to dync for some 2,000 songs. Then next day, 300 songs. The next day, 900 songs. And so forth. I have about 10,1000 songs total with about 2,000 to 3,000 songs synced with my iOS devices at any one time.

I also found that I have been getting somwehat similar weird artwork syncing based on having set the iTunes preferences to share data with Apple and to automatically download album artwork.

Bottom line is that since activating the Genius and artwork settings, syncing has been taking a very long time and I find that the same song titles seem to race across the screen almost every time. I don't make wholesale changes to my library so don't see the reason for all the commotion every time I sync. So I have just turned all this stuff off because it seems to waste more time than is offset by the benefits is provides for me. The "Genius" feature really does not produce any surprises in terms of putting artists together that I might not have thought of on my own. I am not compulsive about wanting artwork for all my albums either.