Hmm, good question, but not so sure. As an "agent" (think Agent Smith), I could imagine instantiating at the behest of some "rule" in an instance of a simulation and then ending your influence, only to pop in again as needed. That would be a deterministic agent with an avatar and certainly not need to live out the life in the sim. As a conscious entity, I could certainly imaging "occupying" an avatar for a period of time if it is necessary to interact with the sim. Don't see why you would have to stay there, though. We normal conscious entities live out our lives because that's what we are supposed to do. But I don't see a programmatic reason that would prevent a "conscious influencer" from popping in and out. And, if you don't need to interact with the sim, I suppose you could always visit, unseen.