Most people buy a carpet the size of the room, wall to wall, and wonder why the place feels smaller the second it goes down. A rug or a carpet needs air around it, floor showing at the edges, or every room ends up looking like a hallway in a budget hotel.
Carpets suit the rooms where you spend slow time more than the rooms you pass through. Bedrooms, especially in a house with cold floors underneath, living rooms where people end up sitting on the floor anyway, a reading corner that gets the afternoon light and could use something underfoot that doesn't feel like stepping onto tile. They do less for me in kitchens and entryways, where life is wetter and messier, though a tough flatweave in a mudroom type space can earn its spot if you choose it for durability rather than looks alone. If you own none of this yet, start with one good carpet in the room you use most at the end of the day, not the one guests see first. A living room carpet in a neutral tone, nothing too pale, nothing that shows every crumb, will teach you more about how you actually live with a floor covering than three smaller rugs scattered around rooms you barely sit in.
How it ages depends entirely on fiber and foot traffic, and wool is the one I trust for a room that gets used daily, it compresses a little, softens underfoot, and still looks decent after a few winters of boots and dropped toast. Vacuum it the direction the pile lies, not against it, rotate it twice a year so the sun and the traffic wear evenly, and get a proper rug pad underneath, which does more for both grip and longevity than anything you spray on top. Spills happen, blot them, never rub, and keep a stain remover made for the specific fiber rather than a general one. A carpet that's had a spill or two and still looks lived in rather than ruined is usually the sign you bought the right one. It sits well against plain floors, against a sofa in a solid color rather than a busy pattern, and against simple wood or iron furniture that doesn't compete with it for attention. Pair a patterned carpet with quiet furniture, and a plain one with furniture that has some shape or color to it, and the room settles rather than fights itself.
If I had to put one carpet down tomorrow, it would go in the living room first.