Does installing a new version of NIS extend subscription date?

I currently have NIS 2010 installed on my desktop computer; there are 50 days left in its subscription.  I recently got a laptop and want to install NIS on that before connecting to the internet.  My NIS 2010 is a 1 computer version, so I bought NIS 2011 3 computer version.  If I install NIS 2011 on my laptop, that will give me a 1 year subscription... but how will the upgrade affect my subscription days left on my desktop computer?  i.e. I do not want to forfeit/waste the 50 days remaining in my subscription there.  Do I just need to wait until that subscription is nearing its end and then start my 1 yr NIS 2011 subscription on both computers?  Or if I install NIS 2011 now on my desktop, will my subscription be extended to 50+365 days?  Thanks for your thoughts.