If a devotee has remained in the company of his Sheikh for a long time without receiving any benefit, he should search for his spiritual upliftment elsewhere. The aim is Allah Ta'ala and not the Sheikh. Care should be taken that one does not become disrespectful and rude towards one’s previous Sheikh. It is quite possible that the Sheikh was perfect, but that the devotee was destined not to benefit from him.
[Ashraful-Uloom, pg. 26] , From 99 Golden Advices for all Saalikeen
NB. Often it is noticed that mureeds do not carry out the advice of the Sheikh nor do they communicate with the Sheikh. In such cases moving from one Sheikh to another will not help.
The advice above is for those who inspite of carrying out all the advice of his Sheikh and still do not progress.