Welcome itsallbollix,
I am also curious about whether one long session is more effective than two back to back with a short break in between. I've always done the former, as it is somewhat difficult to cut practices short when their momentum builds.
Some resources to help address the question:
over-sensitive: meditate once a day?"Three hours per day is enough time to put together a really terrific twice-daily integrated practice routine covering all aspects of yoga, and leading to far greater results than doing any one practice for that duration." -p. 563, Support Forum Posts of Yogani
"So there is a going out to establishment of abiding inner silence (witness), and then a coming back into full action with inner silence. That is the journey of yoga. That is why daily activity is an important part of the over all practice, to stabilize stillness in action. We are not leaving forever into samadhi without objects. It is not a one way trip. We are systematically going out and bringing samadhi back into daily living. So it is very practical." -p. 129, Support Forum Posts of Yogani
