I don't understand- I don't think I will ever get to the point where I will say that. There is no class of knives where I don't already have more than I can use, but I might still buy more if I see something I like. As "collectors", even using a loose definition of that word, we only have to justify spending the money for the item, we don't have to justify buying the item. Buying a knife when you need to make a house payment is not a wise use of your funds and not properly caring for your family, but if you have the funds and you want another to add to your "collection", then that is completely up to you.
As for having more knives than you can use, I've heard people say "two is one, and one is none", IOW if you have one knife for use, and something happens to it, then you have none. And something could happen to it even just moments before you need it. So just based on that you can justify having an extra or two. I've also heard "a pair and a spare", which is the same line of thinking. You have the one that you are using, which could disappear any moment, then your second one would become the first one, and the third one would become the spare.
Interestingly enough I have been involved in collecting wrist watches in the past. I was collecting knives before that and so it became really apparent to me that most wrist watch collectors will want to wear all of their watches, whereas most knife collectors don't actually use many of their knives. I've seen some amazing custom knives that I can't imagine anyone actually using to chop limbs or work on game animals with. But if a watch collector finds that they aren't wearing one of their watches, they are quick to sell or trade it for something that they think they will actually wear. They have a harder time justifying buying more watches because they are limited in how many watches they can wear at a time. Knife collectors can buy knives with no intention of ever actually using them, and as for the ones that they actually use, they can carry more than one at a time even! I also noted that watch collectors are fairly fickle and the watch that they bought and liked to wear yesterday will become old to them and be on the auction block today or tomorrow.
I have been involved in