I recently bought a one-year licence of Office 365 Home. If I now buy another licence and activate it, will the existing licence be extended by 1 year?
Yes, as long as you use the same Microsoft account again, the duration will be extended by 12 months. For example, if you have two months left on your current Office 365 Home subscription and you renew for 1 year (12 months), your subscription will have a duration of 14 months.