They do change, even after you're grown. Size numbering is an imprecise art. Look for a good fit around your heal to limit slippage, an arch that matches yours, and width and shape that conform to your feet. Sounds odd, but smoking constricts blood vessels and can cause circulation problems in your feet. Curved nails are an invitation to ingrown toenails.
Natural fibers absorb moisture best.
A daily stroll is good exercise and improves circulation in your feet. Follow these suggestions, and you should develop a new relationship with your footwear. Sure, you'll still favor those sneakers, but you'll put aside the shoe closet panic.