You don't mention how many pipes you already have. I've got only seven Briars and since I smoke quite a lot, this isn't enough to really let a pipe rest for optimum flavor. Plus, not every pipe has the same bowl size, so some give shorter smokes than others. For my longest smoke, I've got a large G sized Billiard. The shortest is from a Dublin. I dedicate some pipes to English blends, and in some I'll allow OTC blends. Whether ghosting is real or not, I abide by it in practice. Straight pipes are a different aesthetic experience than bent pipes. This is a reason to have both types, unless you dislike one type. Smoking a pipe isn't like cigarettes where every smoke is the same unless you switch brands. Some pipes, you may not want to take out in public for one reason or another. Some might be clenchers and some not. Rustication vs smooth feels different in the hand: another aesthetic difference. There are many reasons to have many pipes. At some point, those reasons aren't going to be sufficient, and you'll want a pipe because it's not like any pipe you already have. The argument will be that variety makes you happy.