How long does a tutor last?

If you mean how long families stay: most stay a full academic year and a good number stay several. The shortest useful engagement is about a term — six to eight weeks will fix one specific topic but will not change how a child works. If you mean how long a booked pack stays valid, unused classes remain usable for six months. And if tutoring has done its job it should end: a child who no longer needs it should stop.