What does this mean?
The agents that we describe in philosophical or mathematical problems have terminal values. But what confidence have we that these problems map accurately onto the messy real world? To what extent do theories that use the "terminal values" concept accurately predict events in the real world? Do people — or corporations, nations, sub-agents, memes, etc. — behave as if they had terminal values?
I think the answer is "sometimes" at best.
Sometimes humans can be money-pumped or Dutch-booked. Sometimes not. Sometimes humans can end up in situations that look like wireheading, such as heroin addiction or ecstatic religion ... but sometimes they can escape them, too. Sometimes humans are selfish, sometimes spendthrift, sometimes altruistic, sometimes apathetic, sometimes self-destructive. Some humans insist that they know what humans' terminal values are (go to heaven! have lots of rich, smart babies! spread your memes!) but other humans deny having any such values.
Humans are (famously) not fitness-maximizers. I suggest that we are not necessarily anything-maximizers. We are an artifact of an in-progress amoral optimization process (biological evolution) and possibly others (memetic evolution; evolution of socioeconomic entities); but we may very well not be optimizers ourselves at all.
Let's say Bob's terminal value is to travel back in time and ride a dinosaur.
It is instrumentally rational for Bob to study physics so he can learn how to build a time machine. As he learns more physics, Bob realizes that his terminal value is not only utterly impossible but meaningless. By definition, someone in Bob's past riding a dinosaur is not a future evolution of the present Bob.
There are a number of ways to create the subjective experience of having gone into the past and ridden a dinosaur. But to Bob, it's not the same because he wanted both the subjective experience and the knowledge that it corresponded to objective fact. Without the latter, he might as well have just watched a movie or played a video game.
So if we took the original, innocent-of-physics Bob and somehow calculated his coherent extrapolated volition, we would end up with a Bob who has given up on time travel. The original Bob would not want to be this Bob.
But, how do we know that _anything_ we value won't similarly dissolve under sufficiently thorough deconstruction? Let's suppose for a minute that all "human values" are dangling units; that everything we want is as possible and makes as much sense as wanting to hear the sound of blue or taste the flavor of a prime number. What is the rational course of action in such a situation?
PS: If your response resembles "keep attempting to XXX anyway", please explain what privileges XXX over any number of other alternatives other than your current preference. Are you using some kind of pre-commitment strategy to a subset of your current goals? Do you now wish you had used the same strategy to precommit to goals you had when you were a toddler?