(and also I love looking at my son with his lightsaber
)My son is one years old and has already seen most of the SW films. Not by choice mind, he's made too by his big ol daddy
Also he now does a pretty good impression of a lighsaber when holding his little toy version. He's seen me with my ForceFX, so now impersonates me with a "wiiiishhhhhh, whooooooshh" which I think is just classic. Good ol' boy
So in answer to your question, they're never too young to watch Star Wars.