It's unfortunate that many people see it as selfish, they can't see that they're being more selfish expecting us to stay through it all for so much longer
Well, except without the living part.
What about the people who suicide because they feel they are a burden on their loved ones? Is that still selfish?
To be selfish, I think you have to be taking something to which other people might reasonably have a claim. If I buy a pie, bring it home and put it in the fridge, then later take it out and eat it all myself, what might make this selfish depends on others' reasonable expectations of sharing in it. If my housemates and I routinely share groceries and eat together, perhaps they can reasonably expect to share in it. If we all buy our groceries separately and don't eat each other's food, then they shouldn't expect to share in it.
So, who has a reasonable claim to our continued existence? A life partner would seem to my mind to have about the best claim, apart from any children that I might have. But then, if you can break-up with or divorce a life partner, it seems unlikely that this should restrict suicide. If we owe care to our children, then it seems they would have a good claim on our continued existence.
One thing that has kept me from suicide has been wanting to be there to care for my beloved cat--thinking of her not knowing where I am really fucks me up. But she has passed on two years ago now.