How many times can you apply for an OPT visa?

My boyfriend is looking to transition from F1 visa to an OPT visa through an employer. This will only allow him to stay in the US for 12 months. Thereafter, he is looking to apply for an H1B. My concern is that if he doesn’t get selected for the H1B, can he extend his work privileges if the employer reapplies for him under the OPT visa?