Just a question re 3 PC Norton IS

I have bought Norton IS 2013 for 3 PC's.  I will put on my own desktop and laptop next week the day before Norton 360 expires. (Norton IS much cheaper than 360).  However, the last licence I would like my husband to have on his laptop but his own version of Norton doesn't expire for 3 months.

 

Does this mean he loses 3 months worth of Norton IS, in other words, do we have to renew on exact same date for ALL 3 computers when renewal is due or wil it know that one computer had later installation than the other two?

 

Hope this makes sense! Grateful for any advice.