Wow! I have gotten two passages back to back before but not three. I can't even recall a student telling me that they've seen this before on GMATPrep.
I agree that that's really mentally draining. First, let's hope that this won't happen on the real test—it's very unusual, so the odds are good that you won't have this happen there.
But, since it did happen this time, I completely understand wanting to be prepared just in case. So let's think this through.
The first passage you would treat just like any other passage, because you have no idea that you're going to get another passage immediately after. So you do the passage the normal way / with normal timing and that may take you to the end of a page in the yellow pad or it may not. (In the case of your last test, it would not have.)
In this case, you would have done the first passage, gotten to Q5, and seen a second passage pop up. Because this is the second RC passage on the same page of the yellow pad, jot down the extra R (I also like to jot down "–2-3m"). Now you know you can expect to be 2-3 min behind on the "normal" time when you get to the end of this page. So far, this is still going according to the normal yellow pad.
But then you get to Q9, the last Q for this page of the yellow pad...and *another* passage pops up! So do the same thing: Jot down another extra R and another –2-3.
When you finish that first question, you're at the end of that page of the yellow pad, so it's time to check yourself against the timing. The target time at this point is 48 with one RC passage, but you've also got to factor in the –4-6 for the two extra passages, so your target time is really 42-44min. If you're within that range, great. You're on track, so just keep doing what you're doing.
If the clock is lower than that, you need to bail on something to catch back up—and you have the perfect opportunity to do that with the passage you're on right now, because you're probably pretty sick of RC at this point.
So on the next question you see that is about part of the passage you don't like, or asks a question that is confusing, or just seems hard or annoying for
any reason—bail
immediately. Pick your favorite letter and move on.
You were at 39 min, so about 3-5min behind—that's two bails to catch up. Just be totally fact-based at this point: Oh, look, I need to bail on 2 questions. Okay, which two? You can make them both RC, if you don't like this passage, or you can take one of them from the RC passage and one from whatever else comes up on this page of the yellow pad. I would do at least one from RC just because your brain is getting tired from doing the same thing so many times in a row. (Strategic note: In general, you save more time by bailing on CR and RC. You don't save a ton of time by bailing on SC, just because those are "faster" types.)
So by the time you get to the end of your second page of the yellow pad, you'll be caught back up. You also won't be quite so mentally fatigued, because you will have chosen to bail on a couple of questions that looked extra challenging for some reason.
Thoughts about this? If you're really concerned about this happening on the real thing, practice this on your yellow pad by setting up a practice set—start with 3 RCs in a row, then do some SCs and CRs. (But, as I said, I think it's pretty rare. The chances are good that you won't see this on the real thing.)