Well now it's time for the 2012 sticker and we decided it was time to scrape off the two old stickers and start fresh, and it's a good thing we did. My husband expected to have the sticker come off in little pieces because "it cannot be removed without destroying it". But, to our surprise...1-2-3...the whole sticker came off in one solid piece. The only thing that got slightly ruined was the 2010 sticker underneath.
So, just as a precaution....Don't believe everything you read and make your life easier by scraping and cleaning off all old license plate stickers. Then use a razor blade and make cross-cuts on the sticker itself. (We did this every year but last year, but now we have learned our lesson!) That way no one can get the sticker off in one piece...guaranteed!