How Long Should I Meditate?
The first rule is, don’t be ruled by what others do. What works well for them may not work for you. Intensity of effort is far more important than the time spent in meditation.
Never meditate to the point of boredom. If you feel joy in meditation, stop meditating when the joy begins to diminish. Don’t force yourself to meditate when you’d much rather be doing something else.
At the same time, be a little stern with yourself. Don’t stop meditating altogether with the excuse that you have other things to do. Success won’t come to people who never try. Read on

www.ananda.org/meditation/meditation-support/articles/how-long-should-i-meditate