Trainers used to be the thing you wore to the gym and nowhere else, and now they're the thing you wear to work, to weddings, to the school run, sometimes all in the same week. Mostly that's been a good shift. It's just made choosing the right pair a lot more complicated than it used to be.
The difference between a trainer that lasts and one that's bin bound by spring shows up in a few predictable places. The upper matters most, whether it's full leather, a treated canvas or a synthetic that's been told to look like either, because that's what decides whether the shape holds or collapses inward at the toe after a few wet walks. Look at how the sole is attached, whether it's stitched or glued, and give it a gentle twist in the shop, a sole that creases oddly or separates at the edge under light pressure will do that forever, just worse. Eyelets and lace tips should feel properly set, not glued on as an afterthought, and the inside seam where the tongue meets the upper is where cheap ones rub a blister into your ankle on day one. A good pair also has some give at the ball of the foot and stays rigid everywhere else, which is the bit that's easy to miss when you're stood still in front of a mirror rather than actually walking.
How they age depends a lot on what you ask of them. Canvas and white leather show every scuff and will need a proper clean, not just a wipe, every few weeks if you want them to stay looking new rather than lived in. Chunkier soles pick up grit and go grey at the welt faster than you'd think, so a soft brush and actual attention pays off. Suede needs a protector spray before its first outing, not its tenth. As for when to wear what, canvas and white leather suit the warmer months and don't love constant rain, running styles earn their keep whatever the weather since that's the job, and leather or chunkier soles carry you through fewer walking) winter outings. For fit, go by the ball of the foot first, not the toe, because that's where trainers actually need to flex, and leave roughly a thumb's width of space at the front. Watch for heel slip, which ruins a style on day one and never really corrects itself, and for narrow builds that pinch across the top of the foot even when the length is right.
Whatever you buy, let them air out properly between wears rather than straight back in the cupboard, it does more for their lifespan than any cleaning product will.