eventually reach a state of static, well defined goals permanently.
First, this is radically different from the claim that an AI has to forever stick with its original goals.
Second, that would be true only under the assumption of no new information becoming available to an AI, ever. Once we accept that goals mutate, I don't see how you can guarantee that some new information won't cause them to mutate again.
Long before goal mutation is a problem malformed constraints become a problem. Consider a thought experiment: Someone offers to pay you 100 dollars when a wheelbarrow is full of water from a nearby lake, and provides you with the wheelbarrow and a teaspoon. Before you have to worry about people deciding they don't care about 100 dollars, you need to decide how to keep them from just pushing the wheelbarrow into the lake.
A stub on a point that's come up recently.
If I owned a paperclip factory, and casually told my foreman to improve efficiency while I'm away, and he planned a takeover of the country, aiming to devote its entire economy to paperclip manufacturing (apart from the armament factories he needed to invade neighbouring countries and steal their iron mines)... then I'd conclude that my foreman was an idiot (or being wilfully idiotic). He obviously had no idea what I meant. And if he misunderstood me so egregiously, he's certainly not a threat: he's unlikely to reason his way out of a paper bag, let alone to any position of power.
If I owned a paperclip factory, and casually programmed my superintelligent AI to improve efficiency while I'm away, and it planned a takeover of the country... then I can't conclude that the AI is an idiot. It is following its programming. Unlike a human that behaved the same way, it probably knows exactly what I meant to program in. It just doesn't care: it follows its programming, not its knowledge about what its programming is "meant" to be (unless we've successfully programmed in "do what I mean", which is basically the whole of the challenge). We can't therefore conclude that it's incompetent, unable to understand human reasoning, or likely to fail.
We can't reason by analogy with humans. When AIs behave like idiot savants with respect to their motivations, we can't deduce that they're idiots.