Depends on where everyone is in their life. An undergrad shouldn’t be dating someone graduated and in a stable working condition. Once your past a certain age, it becomes fairly useless as a question of appropriateness- with things like life experience, goals and present conditions being more important.

even then; it’s about maintaining a healthy balance of power in the relationship. if it’s a one night stand and everyone involved are consenting adults; that’s none of our business.