The first hoodie I bought with my own money was a size too big because I thought that was the point, and it taught me that swamped only looks deliberate on other people. On me it just looked like I was wearing someone else's washing. That one lesson has stuck for twenty years of buying these things.
Sizing is the whole game. Go by the shoulder seam and the body length rather than the chest measurement, because that's where a cheap one tells on itself first, the seam dropping halfway down your arm and the hem sitting at an odd point on your hip. For sweatshirts I size closer to normal, maybe one up if I want something to layer over a shirt. For hoodies I'll sometimes go one size down from what I'd usually take, because the hood and the front pocket add bulk that a true size turns bulky rather than relaxed. Sleeve length is where the tall and the short both get caught out, so check it against something that already fits well at the wrist rather than trusting the size label. A good one should sit close enough at the cuff and hem that it holds its shape, not so close that it pulls when you lift your arms, which you'll notice the first time you reach for something on a high shelf and it rides up at the back.
How it ages depends entirely on the wash, more than most things in the cupboard. The inside gets bobbly first, under the arms and where a bag strap sits, and that happens faster if you tumble dry it every time. Turning it inside out before washing keeps the print or the colour going longer, and drying it flat rather than on a radiator stops the body stretching out of shape while the ribbing at the cuffs and hem stays tight, which is the mismatch that makes an old one look tired rather than lived in. A good cotton one softens properly over months, the kind of soft that makes you reach for it on a Sunday before anything else. A thin one just goes thin, and no amount of careful washing fixes that.
Where it falls apart is in the styling rather than the washing. Worn with anything tailored it reads as mismatched rather than relaxed, a blazer over a hoodie looks like two outfits that got stuck together by accident. Keep it to jeans, straight trousers or leggings, trainers, a simple coat on top, and it earns its place. It's a jeans and trainers piece, a weekend errands piece, not a meeting-the-in-laws piece, however good the fabric.
This suits anyone who wants one thing that works without a second thought on a day when nothing else feels right.