I think the Droid's R2 and 3PO are the ones that bring all the films togather. from there point of view its one BIG Story. with smaller storys around each.
Plus Droid's do not Age.
Sometimes I think it would be Cool 2 be a Droid. Only worrie would be getting your next can of Oil and Spair Parts 10.0000 mile(or year) tune-up and fresh Batteries.