Upgrade from Deluxe to Premium

Hi,

I currently use Norton Security Deluxe, using all 5 out of 5 seats. Now, I have another device where I'd like to install Norton Security. When trying to download from the Norton site, it tells me I have used all licenses and offers an upgrade. So far so good, but as far as I can tell, the offered upgrade is for Norton Security Premium. My main concern is: if I upgrade, can the existing 5 devices continue using their installed Deluxe version, or do I have to upgrade the software on all existing devices to Premium? I don't need the Premium features, just the number of seats, and would like to avoid having to reinstall the software on 5 devices.

Cheers, Robert