I was reading on someone's poker blog the other day that indicated that their extended sessions can lead to declining results. E.g., let's say you typically do a 2 hour session (barring any juicy conditions), and then shut it down for the day. On another day, you have a great deal more time (no HW, etc.) and you extend this to 4-5 hours. Does anyone see a decline in results?

Speaking for myself, I notice that a session of between 2-3 hours of ring is ideal. If I extend past this point, my performance seems to pale, particularly with following occurrences:
- a horrible beat; more frustrating due to the long period if time I've invested in the session ("just lost my profit; damn 4 hours are a waste!")
- my reads lose their sharpness (e.g., might make a couple dumb calls, or start "not believing people").
- A couple good players that I have notes on join the table, and I'm approaching this 3 hr threshold.
- I hit my ~3rd beer

I've been trying to make an effort to shut down for while if I experience these events, so that I don't throw away hard-earned money. In essence, I've been working to protect my headspace.

Seems like common sense, but I think we all know the traps that we can fall into. Just wanted to hear some discussion on inflection points or disciplines used to stop a session...