Either everything is permanent, or everything is impermanent, or some things are permanent and some impermanent.
Universal eternalism—in effect, denying the reality of time—has an illustrious history in Western metaphysics, ever since Parmenides reflected on the absurdity of getting something from nothing. In the canonical texts it often goes hand-in-hand with a kind of exhilaration or bliss; regarding everything as impermanent, by contrast, we often associate with the loss of hope and direction. According permanence to some things and withholding it from others seems to be what we normally do at the pre-reflective level, balancing idealism with realism—though it is notoriously hard to explain how entities of both kinds could exist and interact with each other.
If we grant that at least some things (not necessarily all) are impermanent, thereby according some foundational status to our experience of time, we can then pose the question: How long do impermanent things last? This question seems immediately befuddling, since it appears to admit of any number of possible answers. Maybe impermanent things last for X duration, or Y duration, and so on. But actually the choice is simple: either they last for some determinate duration or for no time at all.
If impermanent things last for some determinate duration and then cease, we can ask why they cease after that duration and neither earlier nor later. But is it really proper to ask for the cause of something's cessation? If cessation requires a cause, then we would need a positive explanation every time something ceases, and this arguably violates both theoretical economy and metaphysical clarity.
In this discussion we will zoom in on the supposed "moment of change", the replacement of one state by another state, and confront the hypothesis that cessation is intrinsic to whatever exists. If it is the very nature of things to stop being, then we have strong theoretical reason to deny not only permanence, but even duration to ourselves, what we know, what we desire, and what we fear.