Keeping oil and gas around for a long time can lead to these fluids going bad, and can effect performance in your snow removal equipment. It is advised that using up snow thrower oil within three years is good practice. Gasoline tends to lose oxidation and deteriorate after six months of storage and will be for the most part useless after 1 year. Allowing air to stay in the canister will further ruin the gas as moisture builds up. Since snow removal equipment is used seasonally, you should attempt to use up any leftover gas in your snow blower before storing the equipment for the off-season.