How long do the effects or results of face lift ...

There isn't a specific set length of time a face lift lasts. Two factors are at play, which are your age and the elasticity of your skin. A face lift lasts approximately 5-10 years. A face lift can only improve sagging skin in the cheeks, neck and jaw line. It's reccomended really only for people in their 40's, because of where skin maturation is at that point. Often times people get face lifts thinking it's going to get rid of lines and textural issues and are dissatisfied after the procedure is done. There are many less invasive procedures that will rejuvenate the facial skin at this time, which give more natural results.

Usually face lift is recommended for those with aged skin. As mentioned by Caitybug, it would last years but only when you follow the required health practices. Most doctors recommend the patients to follow a balanced diet as well as exercises. Some are prescribed vitamin supplements to enhance a natural growth of healthy skin. 

I would say, non invasive procedures are better options. A good choice is Laser skin resurfacing.