I replied this to a different idea, but I think this may warrant it's own heading.
I think instead of multiple seat options, it would work better to have a seperate product, maybe "Webroot SecureAnywhere Ultimate" where a user could protect all of their devices in their household. For example, say I need more than 5 seats. The "Ultimate" product from Webroot would allow me to put all of my devices on it. Maybe position it at a price point of $99. It would also be great if Anti-Theft coudl be incorporated into the PC program for the Ultimate product.
This would be very similar to the McAfee All Access and the Bitdefender Sphere products.