You need to attempt to sit, with time blocked out, every day.

The minimum length of time question is a bit trickier. You will make progress if you are doing some meditation at “the edge of your current skil”. You can see that if that’s true if you are making progress – if your attention is more stable at your next sit (or at most over the next 3 sits).

In the early Stages, that’s pretty much all of the time you are meditating. Everything you are doing is new and causing progress. In the later stages, in can take a while to get to the place where you are exercising new stability.

The maximum length of time question is easier. If you are not frustrated or resentful, you can keep going. Every minute will count. More minutes means faster progress.

For my students, in the early stages, I only care that they are sitting every day. 2, 5, 10, 15 minutes are all fine. Very few can do 15 minutes at the start. Within a short time – Stage 3 – students are usually at 20-30 minutes. Later stages can require 45 minutes. One stage I was in required 1 hr 15 minutes.

If you are having a bad sit, it matters what your mood is. If you are frustrated or angry, stop. If your attention is merely unstable (worse than it has been), you can still work with it. Your are working at the “edge” of attention stability, and that counts, even if that edge is lower than it was previously. These kind of sits often happen when you are sick, or tired, or hungry, or stressed.