employment letter for 3 year and can I apply early

Hi,

I have got 3 earlier 1 year TN visa and now need to get next TN visa(all TNs are with the same employer). What is the difference of employment letter between 1 year and 3 year TN visa except the duration of 3 years.

Also my current 1 year TN is expriring in May 2009 but I want to get the new TN 3 year with the same employer now in March 1st week so is it fine to apply 2 months early. Thanks in advance,

Well you can always abandon your current status and apply for it again, if your job offer letter says you start in March then it doesn't matter.