I was tearing my hair out working with a file using multiple images containing patterns inside snowflakes. Every time I saved the file it got bigger and bigger even when nothing had changed except I was trying to rasterize images which was suggested to reduce file size. Finally after reading many other illustrator forum comments on this issue, someone suggested copying all the content and pasting it to a brand new file artboard. I did this and started an entirely new file with the same artwork, and when I saved this new file it it went from 240 MB to 3.5 MB. Something is clearly wrong in the saving process - I had even done "save as" several times with the same name to prompt the new file to overwirte the old file. It is crazy, like playing leap frog if as I go along to keep a project from getting too big I must constantly copy all work and paste to a new file.