Eh, just like shorter lifespans, eternal life would probably be what you make of it. The only issue might be if you were trapped somewhere for long durations, although even then
Otherwise I'm not sure I can agree with things lacking meaning due to permanence and, I should note, even if you were immortal, you'd still have moments with limited duration. Even within peoples' short lives they have tons of moments, many of which either directly contributed to the person they are today or from which they extracted some meaning. (I guess a comparable example would be somebody who has short romantic relationships vs long romantic relationships. The short relationships would have a direct change in partners (and the people themselves might change over time partly based on those relationships), whereas the longer relationship would see the nature of the relationship change over time. In the scope of things, arguably the longer relationship probably has more meaning since it continually evolved even though the shorter ones have more surface-level changes.)
And in the cosmic scale of things, I suspect that even if people lived forever, they'd constantly change, unless they were stuck in a setting that precludes change.
That's a good way of looking at it. It seems that even if life happened to be eternal, it wouldn't change the fact that we would still create our own meaning or purpose in it. Although, I guess part of my original fear was the idea of living so long that everything around you eventually crumbles and you are all that is left floating in a void of nothingness. Though that is a more specific problem of living eternally as a human in a finite world.