Lifting the neck to create a better angle of the jawline is done by a variety of techniques. Every neck is different and each necklift must be tailored to the patients to include patients goals, risk tolerance, and tolerance for downtime. It is most important to do your research and choose a great doctor, understand the procedure, and clearly define your goals. Time in the operating room should be low on your level of concerns.
Neck lifts are one of the most popular procedures now since they dramatically improve patient's appearance and look natural and tend to be affordable for most patients. They can be done under local anesthesia now which is a major improvement whether it is a mini facelift were the skin of the jawline and neck is pulled back ($6,000) and/or platysmaplasty were the skin under the chin is removed and tied tight ($4,500) or whether liposuction alone can improve the neck a lot with just removal of the excess fat pulling down on the jowls and neck ($2,500) or combination of the above. Time is of little concern when quality results are needed.
So far there are good answers to this question. I would say it really depends on what you need. A isolated submentoplasty may take me 45 minutes to an hour and a simple neck lift 1 and a half hours. A more involved procedure may take several hours. All of these procedures may be done under sedation or general anesthesia. The faster the surgery is not what counts! You want a good result so choose your doctor based on reputation and results! Good luck.