1. First of all, it depends on the civil capacity of the elderly. If the elderly have full capacity for civil conduct, that is, they can understand their actions and their consequences, then the commitment letter signed by them is usually legally binding. Do not have full capacity for civil conduct, in some cases, if the capacity for civil conduct of the elderly is questioned, it can be identified through legal procedures. Interested parties or relevant organizations may apply to the people's court for the recognition of the elderly as persons with full capacity for civil conduct. It can usually be proved by medical evaluation, psychological test or appraisal by relevant experts. For example, a health certificate can be issued by a professional doctor, indicating that the elderly have no mental illness or disorder that affects cognitive ability.

2. Secondly, to review the contents of the letter of commitment, it is necessary to be clear and specific and express the true wishes of the elderly. If the contents of the letter of commitment violate the mandatory provisions of laws and administrative regulations, or violate public order and good customs, it may be deemed invalid.

3. Then look at the signing process. If the elderly are deceived, coerced or misunderstood when signing the letter of commitment, then the letter of commitment may be considered invalid. Of course, this requires evidence. If the promise is witnessed or notarized by a third party, its legal effect will usually be stronger.

4. Then see if there are any relevant legal procedures. Even if the letter of commitment has legal effect, if it involves legal acts such as property transfer, it is necessary to go through the formalities of property transfer in accordance with relevant laws and regulations in order to truly complete the property transfer.

Finally, the legal provisions are different, and different countries and regions may have different provisions on the legal effect of such commitments, so it is necessary to judge according to the laws of the specific place, and it is recommended to consult local professional lawyers.