Is there a secret history to the throne room+duration rule? I've always kinda wondered why it exists. It seems like it made the design of a few cards (tactician, outpost, procession) more complicated.
It goes back to before the cards had "duration" on the bottom of them. Something has to track what you're getting next turn. The duration card stays out because it has "something left to do"; the idea is, the Throne also has something left to do.
In retrospect it would have been better if duration cards not in play didn't do anything (and, if cards you couldn't put into play also didn't do anything). That clears up Procession.
Outpost has an anti-Throne clause. Ideally it would have some form that didn't need that.
Tactician has an extra cost on getting your bonus next turn; that premise requires dealing with the tracking rule, unless the extra cost is something you can always pay (e.g. taking debt).