H1B renewal applicable date after 3 Years.


I have entered USA on L1B for Company A (expiry date = March 2013).

I have changed to Company B as H1B ( expiry date = Jan 2014 ).

I have again changed to Company C as H1B ( expiry date = Dec 2014 ).

I have stamping for Company B (expiry date = Jan 2014 ).

I have got my I-94 as expiry date as Dec 2014 which is latest expiry date for current employer (Company C)

My Question is: When do i need to apply for H1B renewal after 3 Years? Will 3 year be counted as per my first entry on L1B or it is as per my latest H1B expiry date?

Thanks in advance !