It'll only stop when you run out of storage space...
That's the problem with knives... they're small. If you collect, for example, airplanes as a local man does (he owns the Spruce Goose... the real one). He just keeps building and building to house his growing collection.
I have a friend who is an obcessive collector of pinball machines. He's not as wealthy as the aforementioned airplane collector and so he is currently in a bind. He's out of space and in a one-in-one-out mode right now while he tries to figure out some way to get more space. He's already rented a large storage unit and it's full too. Fortunately, for him, the only argument with the wife is about which ones go to storage, not the ones she likes; she's as much a part of the problem as he is (yes, there have been cases where they unknowingly bid against eachother at auctions).
Cars? Again, unless you're very wealthy, you quickly run out of space.
Knives? Well they're small. You can fit a couple of thousand knives in the space of one pinball machine.
I doubt that the largest knife collection in the world is even a fraction of the volume of one Spruce Goose.
My younger brother collects pens; they're more-or-less the same volume has knives. My older brother, coins and stamps which puts him in much worse trouble than either of us.
So, try to find some other object to transfer your interest to, something which is large and cheap.