@Kurtin & Arjan: I believe that the points you have raised are good responses to my objection. In my opinion, the best answer is that immortals take their time doing things.
My main point is that Lara subjugating him wouldn't be the point at which he needed to be replaced. It may have been the straw that broke the camel's back, or it just may have been that it took 30 years to get everything in place (whether that was stars, agents, internal White Court strife, or some combination of some or all of those things). Once he was neutered, he became much less valuable as an ally or an asset because he was much less willing to take action.