If you cannot continue working at the SGA level due to your disabling impairments during the 36-month rentitlement period, you do not have to go through the disability application process all over again. Rather, you just notify Social Security that you are unable to work, and they will restart your disability benefits right away. This safety net is intended to encourage you to test your ability to work.
You only get one 9-month trial work period, and only one reentitlement period.
Trial work and reentitlement are for Title II disability beneficiaries. There is no trial work period or reentitlement period for SSI beneficiaries.
Remember also, when you ask the ALJ for a closed period because you have returned to work, there is no reentitlement period.