Well, 18 pieces is now the most I have heard of one one guitar. However, I have seen a Les Paul with a lot. It was a 20th anniversary model and that had a fourteen piece body. One across the back, a veneer between that and the next lot of mahogany which was 7 piece, another veneer and then a fiver piece top.
I read a lot of people's opinons on lamination, some of which is couched in pseudo science, but I have yet to see any properly researched work on it. There may be some, I have just not seen any.
I agree with the other people though, if you are going to do that much work to a guitar........