As long as you think is necessary for you to achieve what you want from your meditation. If you need a quick brain break while at school or work then a quick meditation is best. If you want a long relaxing detox meditation then perhaps a longer and more in-depth meditation would suit your situation better. Again it all comes down to what you want to achieve.
Answers reflect the personal experiences of Fabulous community members. They are not medical or professional advice — for guidance about your health, talk to a qualified professional.