my teenager may want to change lesson duration after a few weeks. What should we focus on first?

Treat the first weeks as useful evidence. If attention remains strong and goals are consistently unfinished, longer may help; if quality falls well before the end, more time may not be the solution. Teenagers usually respond better when they understand why a particular skill is being repeated instead of feeling that they are being sent backwards. A trial or assessment lesson can help confirm whether the pace and teaching approach fit the learner.