This is a great question. The layers of the face dissected are what determine the efficacy of a facelift. The downward descent of the underlying structures of the face such as the SMAS is what contributes to the aging changes seen.
Quite simply, a facelift is an operation of release and resuspension
A SMAS suspension tightens the SMAS but it does not usually release the SMAS and resuspend it in a favorable position.. A deep-plane facelift is usually performed by an expert facelift surgeon. This involves dissection underneath the SMAS which allows for release of this structure and resuspending it in a natural vector. The best results are usually vertical vector facelifts.
Deep-plane facelifts should be performed by a board-certified facial plastic surgeon or plastic surgeon who is comfortable with this advanced technique. Any revision facelift is more difficult then the first time around but it is definitely still possible.
Best of luck,
Sachin Parikh, MD
Web reference: http://intl-aes.sagepub.com/content/31/8/874.full