Getting TN visa renewed before the expiry date

My TN visa expires at the end of March 2009 and I'm wondering if I can get a new one in December 2008? (I will still have the same employer).
Many thanks!

Can't see why not, you just pay more by applying earlier. The only advantage I could see of waiting would be for them to get up to speed with the new three-year validity period for TN-1, so you get it for three years rather than one.

You can have multiple employers on TN-1, so re-applying while it is valid is normal.