Social Security says:
Q: Is there a time limit on Social Security disability benefits?
A: Your disability benefits will continue as long as your medical condition has not improved and you cannot work. Social Security will periodically review your case to determine whether you continue to be eligible. If you are still receiving disability benefits when you reach your full retirement age, your disability benefits will automatically be converted to retirement benefits.
Some disabilities are reviewed more regularly. If there is a condition that seems irreversible – a stage four metastasized cancer – there will be fewer reviews. A younger person with a psychiatric disability, for example, might be reviewed more regularly. The goal is to review a case eery three years, but current workloads and budget constraints have made that difficult.
If you have a review, get a letter from your doctor saying your condition has not improved. That should be the end of it. Learn more about disability benefits here.