Ds was a great sleeper up to about age 2 1/2 but over the course of the last year it has become progressively harder to get him to fall asleep to the point at which one of us has to sit with him on his bed until he is asleep. Some nights this can take nearly 2 hrs. I try walking out but that results in hysterical crying that the neighbours can no doubt hear. Any thoughts on strategies to get him back to being able to fall asleep alone ?