Glad to hear you made it through P3 without too much angst. ^_^
If you are doing the protocol the way it is intended, you always do 40 day rounds until you get to the last one, and then finish off with the shorter round for the last 15 pounds or so.
People on the forums seem to have good success with doing an interruption (4-13 days) after 23 injections and then finish up the remaining 17 dose days afterward. If you plan for that, you can decide to end at 23 days anyway. It leaves your options open.