You are allowed to stay only 5 years total in L-1B status in the U.S. - so after the first 3 years, you would be able to extend only for 2 more years. Perhaps you would qualify (or had applied) for an L-1A, which would give you additional 2 years. Otherwise, the clock will restart after spending 1 year abroad.
The maximum on L-1B is five years. That only gets reset after spending at least one year outside the US.
J Charles Ferrari Eng & Nishimura 213.622.2255 The statement above is general in nature and does not constitute legal advice, as not all the facts are known. You should retain an attorney to review all the facts specific to your case in order to receive advise specific to your case. The statement above does not create an attorney/client relationship. Answers on Avvo can only be general ones, as specific answers would require knowledge of all the facts. As such, they may or may not apply to the question.