transfer wife's H4 to new employer after travelling to US?

I’m on H1B visa, I have changed my employer from A to B I’m married and my wife travelled to US on H4 visa sponsored by employer A her visa is set to expire at end of 2014 Should I transfer her H4 to employer B? if so when should I do the transfer?

I want to know this as well.

H-1 is rigidly employer linked and H-4 is just as strongly linked to H-1. She can continue on this H-4 as long as it is active but I would not wait that long. This is because If your wife tries to change status or extend her H-4 at last moment, her H-4 documents and your present H-1 documents will not match. If you plan to stay in the US, I suggest transferring the H-4 to employer B now. It is a silly formality but will give you peace of mind.