The silliness of the trope starts with the notion that once you have gone immortal you can't go back. Somehow you are stuck yearning for the sweet release of death.
In reality life is extremely fragile, maintaining the right conditions to support it requires constant effort. There is no reason to think that any future scientific advance will alter this fundamental fact.
Therefore it is highly likely that whoever achieves practical immortality will be also able to undo their "curse" by simply discontinuing whatever practice keeps them alive.
Also, "forever" doesn't happen all at once. Give me immortality, and then check in with me yearly if I still want it. I will let you know once I'm over it.