It has never been about a certain number for me, I really don't know how many I own. I know I have some I never use I just enjoy the craftsmanship and the aesthetics of the knife, others many others I use. Your opening post used the word"collection" which means an accumulation, there is no finite number. As a collector and user I buy knives that I like or has some collectability to it.
I have areas I like in fixed blades, traditional folders, flippers and just interesting knives. The important thing is I have never sacrificed family financial obligagations to my hobby. I am to the point now I can either sell or trade off a knife (rarely) for something I don't have.
We are not unique in our hobby, every other serious hobbyist does the same thing be it collecting marbles, automobiles, purses, stamps, coins, you get the idea. First and foremost do what you like in this hobby there are no set rules dealing with numbers you own, but above all else just enjoy!