Chains, bearings, tires, cables, grease, lube and bar tape need replaced a number of times each year. If an item wears out in a year or less, I keep the item in stock
Steel cassettes (SRAM Red) last me around 30,000 miles and chain rings longer still. I don't generally stock these.
I've never worn out a stem, handlebar or rims. I have broken lots of stuff including steel, aluminum, and magnesium frames. For instance. potholes love to consume my aluminum rims but they have never killed any of my carbon rims. So, I just use carbon rims now.