Keep momentum every day, or get closer to retreat-level concentration but only occasionally? I don't think that there is a universal answer to this question. Consistency is nice to have, and so is building a steady habit - however, the depth and momentum you build with longer sits is also a very precious thing to benefit from.
For the Fire Kasina specifically, given that it requires a rather delicate level of concentration, I believe that many participants would benefit more from a four-hour sit than from two two-hour sits, but with these things YMMV.
Perhaps more importantly: The FK à la Daniel seems to work much better during the evening and night than it does during the day, so timing might be a more important consideration than time.
Possible compromise. The premise seems to be you that can allocate 2 hours a day on average, but are flexible as to when to do that. So if we are looking at a total of about 14 hours a week, you might try something like:
- Monday: 1 hour,
- Tuesday: 1 hour,
- Wednesday: 1 hour,
- Thursday: 1 hour,
- Friday: 2 hours,
- Saturday: 4 hours,
- Sunday: 4 hours.
This schedule might give you the best of both worlds: Depth and momentum during the weekend, and keeping baseline levels of concentration throughout the week. A more extreme version of this might be 1 hour a day 6 days a week + an 8 hour mini-retreat once a week, if work, family, and social life permit.
Do let us know what you try and how it works for you!
