I don’t have experience with this but I’ve read various things on this. Some claim hair doesn’t grow as well in previously transplanted areas due to scar tissue but I’ve seen enough cases of touch ups and density enhancements where I don’t think the issue is that big of a deal. I’ve also heard the second transplant in the same area can grow slower than the first.
however, like spanker said, if you go to a reputable surgeon and youve already experienced good results last two times, I wouldn’t worry too much
good luck