Many points to ponder.
How do you feel about "silhouettes" in terms of change, vs just having more of similar items?
I'm finding I want to be able to explore different cuts in clothing--more or less taper, longer or shorter, that sort of thing. Then I tend to start to feel better in certain styles and not some of the older ones. Then I run the risk of over-stocking in the favorite shapes which might not be favorites later.
So, in addition to numbers of items, I think it's interesting to look at picking 3 or 4 "silhouettes" which are kind of capsules, and then having enough of those.
Also I think I am not a "stock up for winter" or whatever person. I don't want to be "set". I'm trying to repeat when I feel that the weather or the styles are not where I want them so I wear what I like of what I've got, and then be able to buy when the item comes along that really fits me. That can mean not on sale, or it can mean buying something mid-season.
The thing about boredom is, you have to be able to tell whether you're bored with something because you're tired of it altogether, or whether if it's in your wardrobe but not in rotation it'll still feel fresh when you do wear it. Does that make sense? Because if the former, you may want to wear and wear and then do one-in one-out and really plan for many seasonal refreshers, while the other you can have a larger wardrobe but wear something, concentrate on a few capsules in rotation, wear something just a few times a year and really enjoy it.
I'm having trouble with the latter because I feel fashion is fickle or that I'm changing faster than I thought.