Lou, DH and I have had this discusson a few times in recent months. During my stim cycle a couple of months ago I felt like I had lost the plot and didn't want to do it anymore. All the drugs, the appointments, early morning trips to the clinic, and not to mention the waiting...it was taking it's toll on me. I told him that once we have no frozen embryos left I didn't want to go through another stim. I've done 3 now, and 2 FET's with 3 frosties waiting.
I completely understand where you are coming from when you say you dont want to give up, but dont know if you can continue with it. The worst part is that there is no right or wrong answer as everyone is different. A few months ago I just wanted someone to tell me to stop, tell me what to do. Of course no one would! lol
Now that I have had a bit of a break and will continue on a break until about Feb, I feel I can handle more if I need to. I don't think I can put a number on it. I just think it is important to put yourself first and take breaks when you need them. I've learnt that for me, doing back to back stims is not a good idea.