Extending your disability benefits depends on the source of your benefits. If provided by individual disability insurance, there would be no extension of benefits beyond the stipulated benefits in your contract.
If you are referring to a re-qualification process, you will need to check out the information found in the policy document to determine what requirements are needed of you to continue benefits.
Unfortunately once a policy is underwritten and placed in force by the insurance carrier, no changes can be made to the contract by either the insured or the insurance company. You will have to apply for another disability policy in order to change any portion of the plan. If you are disabled and drawing benefits, the contract will only pay to the contract limit.
If you are referring to a re-qualification process, you will need to check out the information found in the policy document to determine what requirements are needed of you to continue benefits.