I have three 890 Pro's and two extenders, here's how it works: each 890 Pro has the same set of activities, divided into rooms. On your remote you select a room first, then you have the list of activities available in that room. If you have two remotes and put them both in the same room, the remotes DO keep track of the state of the components.

If you start an activity with one remote, nothing happens on the other remote's screen. However, you can then select the same activity on the second remote, and it'll "join" that activity because it knows everything is already turned on. Then you can actually control your components with either remote.

Then when you're done, you can press "off" on either remote and that remote will shut everything off. The other remote will still be on the activity screen though. But if you press "off" on that other remote, it knows everything is off so it won't send any off signals again, it'll just return to the activity screen. Of course, when you have both remotes on the same activity, you can just hit the "activity" button on one of them and then put it away, you don't have to do "off" on both remotes when you're done. The only thing is that might be a little confusing because you might at some point pick up that remote again and find it still on the activity screen when it's not really in that activity anymore.

I hope that wasn't too confusing.