H4 tranfer require stamping again

I have transfered L1 to H1 visa and I got approed this year 2013, we are planaing go to india trip in Oct month, and get stamping in oct month.

In Oct 20th I am returning back to US, but my family will be return back in Dec month.

So, In middle I am planing to transferred my H1b  to anthor company in Nov month.

Do my wife need to go for Visa stamping again?

If they already have valid unexpired H-4 visa stamp, then no new stamping is required. They can enter US using the old visa stamp and copy of new approved petition.