Ben Bradley's main argument for hedonism (in his recent diavlog with Roy Sorensen) seemed to be that other theories run into "difficulties" when it comes to specifying when certain alleged harms occurred. For example, most non-hedonists think that achieving your goals makes your life better. But suppose that you work hard to preserve a great work of art, only to have some vandal come along and destroy it after you die -- making it so that all your hard work was in vain. I think it's clear that this is bad for you, but Bradley asks, when is it bad for you? Roughly: "It can't be bad for you when you're alive, since your desire isn't thwarted yet, but nor can it be bad for you once you're dead, since you no longer exist to suffer harms. So it can't be bad for you at all."
I find pretty much every step of that argument dubious. Note that the first premise is technically false. Time-indexed propositions (e.g. "that the artwork survives beyond time t1") have their truth-values timelessly, so if you currently desire that the artwork survive beyond future time t1, and it doesn't so survive, then technically the desire is ("already") thwarted, in virtue of this future state of affairs.
The second premise is also dubious in light of 4-dimensionalism, as Bradley himself acknowledges and relies upon in explaining why death itself is bad for you. (Even after you die, you nonetheless exist in the past, and so the fact that your life wasn't longer can be bad for that past entity. And I doubt much really hangs on the metaphysics; presumably even presentists would want some way of saying things like this.)
Most importantly, it isn't at all clear why we should think that harms must have a temporal location at all. A harm is just whatever makes your life worse (less desirable). There doesn't have to be a particular time at which it is worse. Bradley's conclusion would only follow given the additional assumption of welfare atomism, i.e. the view that the welfare value of a life is simply the sum of the values of each individual moment. But there's no good reason to grant this assumption (especially for non-hedonists). We should instead be value holists, as I argue here. (See also Parfit on Global Preferences.)
(It's odd; in the discussion of the "James Dean paradox", Bradley effectively notes that the vast majority of people are in fact implicitly committed to value holism. We think that the overall 'shape' of the life matters, rather than only caring about the sum total of happiness contained therein. Bradley just dismisses this as "irrational", without argument.)
Indeed, even if we're hedonists, it seems that negative facts -- like the fact that you didn't get to live longer or experience more in the time that you had -- can be undesirable for your sake, and hence qualify as 'harms' in the broad sense of the term, even though these are 'global', atemporal features of your life. And on every plausible view, we can be harmed by events that take place before we're born. It doesn't seem that much of a stretch to acknowledge a similar phenomenon in the opposite direction.