I've never brought them mountaineering, but bring them religiously on mixed alpine routes. Anyway, I usually bring anywhere from 3-5 pins, depending on terrain/rock.... bugaboos and knifeblades being the mainstay, maybe 1-2 lost arrows, maybe a baby angle in place of the larger LA. A deftly swung pick can often weld a small stopper in a placement for an LA or baby angle, so maybe just bring a bugaboo or knifeblade, but again for general mountaineering I don't see the weight justification.
check out ushba's titaniums, generally carry 4-6; and 3 blades. Really ideal for those dime-thin seams.
Mark, do you regularly climb with the Ushba pins? How reuseable are they? I used a couple ti pins about 15yrs ago (not Ushba) and those suckers were like the soft steel pins of yesteryear.... meaning they got welded in place easily, or only had a handful of placements in their lifespan because of the amount of abuse it took to get them out.