For that particular show, yes it did make some story sense to kill off that character, although I do think recasting him would have been an option. By the end of season 2, his ageing was definitely noticeable, and the producers have a 5 season plan, so assuming that's what gets made, it would have looked out of place by the end, so he would have had to have been recast to be plausible in any way for the age the character was.