The friendship with Shaikh has no other motive than guidance in seeking God. As long as your individuality lasts it will last, as long as you are seeking God it will last, as long as a guidance is needed it will last. The friendship with Shaikh is called Fana-fi-Shaikh, and it then merges into the friendship with Rasul. When the mureed realizes the existence of the spiritual qualities beyond the earthly being of the murshid, that is the time when he is ready for Fana-fi-Rasul.