I would like to know if it is easy to obtain a work permit once a WHV expires as I am not 100% sure how it really works.

I am currently on a WHV which is to expire on 4th Feb 2011. My current employer wants to keep me on for another 2 months. Can I apply for a work permit to cover those 2 months? Or can I just apply for a permit for up to 3 years so I can look for another job after that???

Also - does anyone know when it is the best time to submit a work permit application to NZIS?