This is an area that is generally plagued with ambuiguities and inconsistent usage. - which makes it even more important to be clear what we mean. I think this will usually this will require the use of adjectives/modifiers, rather than attempting to define already ambiguous words in our own idiosyncratically-preferred ways.

Instantaneous vs. life-time (or smaller life-slice) utility seems to make a clear distinction; decision-utility (i.e. the utility embodied in whatever function describes our decisions) vs. experienced utility (e.g. happiness or other psychological states) seem to make clear-ish distinctions. (Though if we care about non-experienced things, then maybe we need to further distinguish either of these from true-utility.)

But using "utility" and "happiness" to distinguish between different degrees of time aggregation seems unnecessarily confusing to me.