I currently have a holding zone for possible donations & alterations. Since I now live in a relatively mild climate, I can get away with keeping things in my closet year round (winter gets cold but not so much that I need a special puffer & snowboots - a warm jumper layered under a coat is usually enough). So I operate under the assumption that, if I don't reach for an item for X months, it should be safe to get rid of (but I've packed my UK winter specific items in a suitcase, since they're obviously an exception here).
That said, I do hold onto items in the 'long & lean' silhouette because, although I've mostly switched to 'crop/ tucked top + maxi skirt' in recent years, there are just some situations which call for slim trousers instead (mostly practical/ lifestyle-driven reasons). I'd feel a bit exposed wearing those pants with crop tops (!), so I keep a handful of long cardigans & tunics for the job, even though I'd also feel a bit 'dowdy' wearing those over my current maxi skirts/ wider leg trousers.
I've already purged any particularly ill-fitting long toppers (so I know the ones that remain will still work) but am also cautious not to over-edit, since it's currently difficult for me to find more slim long cardigans at retail (seems the trend now is chunky/ shacket?)