My children, now in their late 20's, saw their father once or twice a year for much of their childhood due to him living abroad. Not ideal but far better than not knowing him at all and they still see him and have a relationship with him now. Surely that has to be better than children becoming adults and not having a clue what their dad is up to it ever seeing him? It does sound from what you say he's not making much of an effort but I honestly believe something's better than nothing. Also, slightly different but there are thousands of kids with fathers serving in the forces whose dads go away on tour for often six months at a time. Is it not worth them continuing their relationships either? Of course it is, it's not ideal but it's what it is. I know it's different from what you describe but no contact cannot be the best option.