I have a long term wish list, usually things that I know will be around for months if not years, sometime specific item like Sezane Chlo blouse in green or generic like navy cashmere sweater. I save them on Pinterest and sort of refer to them if anyone asks about gift ideas or to help budget to buy myself.
But I constantly get side tracked - new items I see in stores, or something beautifully styled online, photography in Vogue.
I have a lot more disposable income now with age and sometimes it actually makes me less careful with my purchases. My biggest error is buying several colours of something and either falling out of love with them or finding they do not last as well. E.g. M&S merino has shrank but not Uniqlo, and visa versa with cashmere.