M.P.
You are right, your labor/delivery is entirely your decision. I think maybe you should as your doctor when is "too late" for IV meds...since they were the ones who told you it was "too late" in the first place. Each doctor is different and each one will tell you when is too late. I asked my dr. when was too late for an epidural and he said it is never too late, the problem is timing the epidural procedure in between contractions that are too close or so late in the labor process that I am already so uncomfortable that it is more difficult/timely to get epidural in.
My experience - they would have given me more nubain, however, it only lasts a certain amount of time and each time you get more, it is less effective (or so I have heard)...I only had one dose of nubain and then went for the epidural because it was getting late at night and the anesthesiologist was available! :-) My experience, the epidural helped my labor progress. 45 min after the epidural, I was ready to push (was 2-3 cm at time when Epi was inserted). But I really held out for the Epidural. I prob would have waited but the nurse "sold" the idea of doing it then by telling me the anesthesiologist was available and if I wanted it in an hour, he might not be available then. Also, had I not had the Epi, there was a good chance of C-section because I was not progressing/dilating.
Also our experience - we did not have a specific birth plan. Our doctor never said those words!! So when I read about birth plans I have to chuckle! I understand there are things that you would like to happen a certain way, but nature works its course. I would have rather not had pitocin, but my water broke and 8 hours later, I still was not having contractions. So, instead of sticking to a strict "birth plan" I was able to stay flexible. Maybe your doctor pushes for a birth plan, which is great. Ours didn't, and it helped me stay flexible and accept the unexpected :-) GOOD LUCK!!!!!
Also, YES, a badly timed epidural can stop labor and sometimes to the point where even pitocin won't help and then your only choice is a c-section. Contractions are NOT fun...but it is part of the labor process. Nubain does make you feel very woosy - a lot of people don't like that feeling. I also encourage you to do your own research. Ask around - other doctors, nurses, even online. Don't simply listen and take ONE doctor's advice. Take control of your experience by researching and asking your own questions!!! (much like you are doing now...but also ask medical professionals their definition of "too late")