When considering how long a face lift should last one should consider the aspects of that question.
First is how is the face lift performed. If it was performed by a board certified plastic surgeon then the technique used was most likely a good technique. If the support structures of the face were correctly addressed and everything was lifted back up in the proper manner then a well performed face lift is supposed to last approximately 10 years. The other aspect of this question is how well has the patient taken care of his or herself after the surgery.
Sun exposure, smoking and an unhealthy lifestyle all lead to a poorer post operative result and potentially the need for more corrective surgery in the future. But the general rule of thumb is that a well performed face lift should last approximately ten years.