Complex sentence: Timothy Leary was a long-time cryonics advocate and signed up with a major cryonics provider; he changed his mind, however, shortly before his death, and so was not cryopreserved.
Split into simpler sentences: Timothy Leary was a long-time cryonics advocate, and signed up with a major cryonics provider. He changed his mind, however, shortly before his death, and so was not cryopreserved.