Well, I don't have as many lenses as Mark. Or time to type my inventory, small though it is. Focal lengths in hand for formats larger than 24x36 are 38, 44, 47, 58, 65, 76, 80, 95, 100, 101, 105, 120, 127, 130, 135, 138, 150, 152, 160, 180, 203, 210, 240, 258, 266, 300, 305, 360, 420, 450, 480. Multiples at a number of focal lengths. Macro lenses that will cover large formats are 18, 25, 40, 50, 63, 72, 100, again with multiples and I've probably forgot a few.
I've pretty much stopped acquiring lenses. I think I can live with the gaps between the focal lengths I have. And I have way too many normal lenses for 2x3, a few of them lovely ex-Soviet artifacts that are completely unusable.
Another impediment to acquisition is that there's a limit to how many I can carry with me when I go a-shootin'. Ole Tjugen, who's been silent in this thead for a while, has reporting having many, many lenses in the same focal length. I went through a phase like that, held shootouts, ... What I learned is that as I shoot 'em good lenses are all nearly enough equivalent. The only problem has been finding good ones that I can afford ...
I have a neighbor who's a serious collector of Zeiss gear. He has a display case with more than a dozen Contaxes, each with a 50/1.5 Sonnar. Also more lenses for formats larger than 24x36 than I can imagine, including a few that I seriously covet. Namely and to wit, 35/4.5 Apo Grandy, 45 Biogon, 53 Biogon, a heap of 75s, a variety of longer f/6.3 Tessars, huge triplets, Super Angulons in many sizes, ... Yes he has 38 Biogons, but so do I. When I need that kind of inspiration I go over and look at his heaps. They're sooo much bigger than mine.
Ian, on a more serious note, I take it your Hexanons are GRIIs. I gave away my 150 because it was a bit too flary, keep thinking about retiring my 210, which is a very fine lens, in favor of a 210/7.7 Dagor type that's smaller, contrastier, and not quite as sharp wider than f/16. How well do your Hexanons shoot?