If you're struggling to figure out how long your lessons should be, you can use this guide to help you figure out what lesson length is right for you:
15 min - Because of the short time frame, only technique is taught in these lessons. This lesson length is good for those who are teaching themseves or playing their instrument in school. These lessons would reinforce good technique and allow you to learn pieces on your own.
30 min - This lesson length is good for younger students. When teaching young children music, it is important to create a habit in and out of the lesson. Having a longer individual lesson will make it harder to focus and they will not retain as much from what they learned. Having lessons every week is also important to build up their knowledge and it makes it harder for them to forget what they learned. For really young children under 6 years old, what I would recommend is 15 minute lessons twice a week. This works with their attention span and reinforces what they're learning more often.
45 min - This lesson length is for students who feel they cannot commit to a full hour lesson, either time wise or financially. These lessons will function the same as 60 minute lessons, however, not all technique or repertoire will be covered every week.
60 min - Having an hour long lesson is good for students who are serious about learning their instrument. This time allows for full teaching of technique and repertoire every lesson. For older students and adults, this lesson length is still effective with lessons every other week.