I did 3 away rotations, but only because my school does not have a home program for me. I was really burning out, though, by the third one. You may think that it will be no problem because you are so excited to go into ortho, etc, but after about 3 months of kissing *ss ALL the time, always having a smile on your face, even when you're doing total scut, and just trying hard not to do anything that makes you look bad/stupid, you WILL be tired. Trust me! Don't get me wrong, my ortho months were great, but they are very exhausting at the same time.
So, with one rotation at your home program, I would not recommend doing more than 2 aways. I think the most important thing is careful consideration of where you do those aways. Quality is more important than quantity. Looking back at mine, I regret one of my choices because in reality it was not really in a location that I want to be in, so I utterly felt like it was a wasted month and that I would have used it better to be at a program that I REALLY want to be at.
As a third year, it is hard to really know what you want in a program and thus what program you REALLY want to be at, (I guess that was my main problem) but use this website to your advantage and try to do your rotations at places that you would love to match. My only other advice is to apply early to be sure that you get the rotation spots that you want.
Good luck... :smokin: