I'm wondering simply whether there is a difference between two thirty minute sits daily and an hour long sit daily? Which is more advantageous?
The single, one hour sit. The other option is far inferior. There's some apocryphal story going around...I think Ajahn Brahm might have talked about it. Or maybe it was Thich Nhat Hanh. Essentially, imagine yourself sitting beside a forest pool. You sit there in stillness, quietly. At first, there's a horde of mosquitoes buzzing and biting. But yet you remain motionless. Eventually, they get bored with you and fly off to trouble, I don't know, a water buffalo or something. Yet you remain, still and quiet. Next, some sort of song bird lands in the tree next to you. At first, he was a little shy. You came in making all this booming racket and you scared the bejesus out of him. But now that you've been quiet, he lands nearby and starts singing his song. After a time, he leaves. Next, a deer comes and starts drinking at that forest pool. Deer are skittish and there is no bloody way this animal would have gotten within 50 yards of you in the state you were in when you first arrived at the pool. The damn thing could feel your agitated energy from across the forest. But now, as you sit still and quiet, he barely notices your presence. And now you wonder...what other creatures are still waiting in the forest, undiscovered, that might emerge as you continue to sit, still and quiet?
This actually works in the woods, by the way. If you've ever gone hunting, there is a spectrum of creatures that you will see dependent on how much of a disturbance you're making. Once you pick your spot and sit down, it takes about a half hour for animals to start ignoring you. The same goes for meditation. The first thirty minutes is just a warm up. Nothing interesting happens during that time. The next 30 minutes, productive things start to occur. But really, it's not until you've sat for 90+ minutes that the real meditation happens.
For longer session:
For 2 sessions:
Now 2 half-hour session vs 1 one hour session is difficult to say, but generally, a half-hour is not long enough to be productive and with only one session, on the other hand, it is difficult to say if there will be a productive session during the day.
The best is to organise one's session as: