Light bulbs always seem to blow at inconvenient times – late at night, during guests, right when you’re about to start work. If you don’t have spares, you either sit with a dark corner or rush to a shop.
Keeping a small stock of the common types you use – say a couple of 9W warm LEDs, a tube light, or specific spotlights – means you can replace them instantly. It takes five minutes and you’re back to normal.
You don’t need a storeroom full of options, just two or three of each frequent one. It’s low-cost insurance against annoying, avoidable darkness.