Babies need to feel safe and secure and they need our help to calm them to a level where it is easy to fall asleep. The close contact and movement of rocking meets all of these needs. In time all babies will grow out of the need for rocking, the question is whether they outgrow this need before they become too big and heavy for the parent to rock.
There is no evidence that shows rocking, holding or feeding to sleep is damaging in any way whatsoever, whatever age the child is. There is no evidence that shows feeding at night (beyond an arbitrary age) causes long lasting sleep problems, or any others for that matter.