We want everybody who connects for live, one-to-one support to get the help they need without having to wait in lengthy queues, so in order to do that we have a 'Fair Use' policy.
The policy allows you to work through your question with a subject specialist until you've understood the concept, but if the session goes past your 'Fair Use Limit', the specialist may ask you to end this session and rejoin the queue to ask a new question.
Your Fair Use Limit may vary - but is shown on your account home page underneath the 'Connect live' button, as follows:
You can see in the above example, that this student's Fair Use Limit is 30 minutes. If they were working through a problem and understood it in 20 minutes, they'd be able to ask another question. However if they understood it at 32 minutes into their session and tried to ask another question, they may be asked to reconnect so that the next student waiting in line can get the help they need.