You can never have too many spare parts. As long as they are kept organized it’s a great resource. Going to the store every time you need something wastes time and ruins project flow. I have stock of zip ties, tape, glue, Arduinos, resistors, capacitors, mosfets, diodes, screws, nuts, bolts, rivets, helicoils, paint brushes, gloves, solder, wires, crimp connectors, heat shrink tubing etc. You get the idea.