This is a very interesting discussion!
The age of items in my wardrobe (most of my things are secondhand so they will already be "old" in some sense) is not something I think much about. It's not part of my mental categorization of clothing items and I would be hard pressed to estimate what percentage of items have been in my closet for what amount of time! I don't disagree with the age class rubrics that many people are posting here but it just honestly wouldn't occur to me to think about things that way. Not a judgement, just fascinating!
I like to conceptualize my wardrobe in seasonal/time of year capsules, so during our dominant cool season I am only wearing a subset of my weather-appropriate clothes at a given time. I do notice that if I wear an item a lot in a short space of time (several weeks) I feel sick of it, but I am generally glad to see that item when the season comes round to wear it again. That is my "likes" remain relatively stable from year to year.
I do feel that keeping clothing for a long time IS a goal of mine. I have a bit of a scarcity mentality around clothing, and tend to feel anxious about an item I like wearing out and not being able to find a replacement. (This isn't really rational -- if nothing else I have enough clothing that I can do without any given item -- but there you go.)
I do sometimes go "off" an item or category of item but have some intuitive sense that it is temporary (currently: tunic-length shirts) and will also sometimes be "over" or move on from things (most recently: unstructured open cardigans -- honestly they were never really all that great, they were just available and I didn't have a sufficiently refined sense of my preferences).
But I think both of those feelings are different than being "bored" of something.