Is a contract extending for the lifetime of a company, which stipulates that dismissal or change of position is not permissible except in specific cases, considered valid or void, especially according to the Shafi'i school, in light of the company's desire to terminate it on the grounds that it is an unlimited-term lease contract?

For the validity of a lease (ijarah (definition)), the contracted benefit must be known. It is known either by the duration or by the work. Otherwise, the lease is void. This is a matter of agreement among the madhhabs (schools of thought). Therefore, a contract that stipulates perpetual leasing is a فاسد (corrupt/invalid) and مفسوخ (nullified) contract.