it probably still would consider time

Is this a mathematical argument, or a verbal argument?

Specifically, what eli_sennesh means by a "planning gradient" is that you compare a plan to alternative plans around it, and switch plans in the direction of more reward. If your reward function returns infinity for any possible plan, then you will be indifferent among all plans, and your utility function will not constrain what actions you take at all, and your behavior is 'unspecified.'

I think you're implicitly assuming that the reward function is housed in some other logic, and so it's not that the AI is infinitely satisfied by every possibility, but that the AI is infinitely satisfied by continuing to exist, and thus seeks to maximize the amount of time that it exists. But if you're going to wirehead, why would you leave this potential source for disappointment around, instead of making the entire reward logic just return "everything is as good as it could possibly be"?