So, I'm going for the Wild Card ending, but my character is continuing to work with House for as long as possible, on the theory that his rule will go much smoother if he lets House more or less finish laying the foundations before swooping in and taking it from him. However, I'm a little concerned that if I go on working for House (which necessarily requires not killing him), I'll go too far and get locked into working for him until the end of the game. So I guess my question is this: when is the best time to stop taking House's orders so that you've more or less done everything it's in your interest to do but you haven't locked yourself out of killing him?

(For reference, I just got the assignment to wipe out the Brotherhood of Steel.)

I'm pretty sure you can kill him whenever you want, but I don't really know.

You can't get locked out of the Independence ending. You only commit to an ending if you start the Battle of Hoover Dam.

Of course, working for House means you won't be able to pursue the Legion or NCR endings (past, I think, dealing with Omertas or the White Gloves; you get two special "quests" that will inform you that you will be black listed, unable to do main storyline quests for the other factions).

Independence is always available, in accordance with Sawyer's "The Game Must Be Completable In Some Way Even If the Player Is a Bipedal Flamethrower Spewing Napalm Every Time He Opens His Mouth" philosophy. Which is an awesome approach to design, Bethesda should learn it.