3 pc subscription update question - one has nis 2009 and the others nis 2010

I just purchased a 3 pc update from nis 2009 to NIS 2010 and on 2 PC's I updated to NIS 2010 and installed the key. In my third PC my daughter opted to stay with NIS 2009 for now since she is doing school work and needs a backup first. I applied the new ket to the 2009 version and the same subscription time 366 days was applied.

 

My question is, can I upgrade to the 2010 version at any time and maintain the subscription?

 

Thanks

 

Kevm