The single best reason why SSDI can end for a benefits receiver: The recipient’s condition improves.

SSDI recipients will receive SSDI benefits for as long as a disability
keeps them from working.   The law requires the SSA to review their cases and conditions on a regular basis to ensure the right benefits are being distributed to the right people.
A doctor is a crucial point for the SSA to help determine the situation.  If the SSDI recipient’s doctor expect their disability to improve, the SSA will check in six to 18 months after it approves the
claim. Even if there is a chance for improvement but not expected, the SSA will revisit the case roughly every three
years. If a doctor does not expect any improvement at all, the SSA will look back into the case after seven years.

It is the responsibility of the recipient to inform the SSA if their condition improves or if they go back to work.