Oren pretended :
On Wed, 23 Dec 2015 16:06:59 -0600, Mark Lloyd
wrote:

I have 2 W10 installations. One is an update from W8.1, and shows as
activated. The other is a clean installation that shows as not
activated. Both have been there since summer. There seems to be NO
difference in the updates available and installed on them.

Don't you need to activate in a certain number of days?

I didn't. I ran W10 for several weeks without activating.