The mantra meditation we practice is limited to 20 minutes. I was wandering why this limitation, is there a reason behind this? Would it be possible to extend the duration? What reaction would be expected. I'm wandering because in old times sages use to meditate extended periods of time. Were their mantras diffrent?...technics? I've red somewhere that there are two types of mantras : mantras for householders (like us) and mantras for people seeking the solitude. Can anybody shed some light on this matter?