Gasoline - Forget it except for little portable units that you drain down after each run and fill with fresh gas each use. Gasoline quickly destabilizes and forms 'varnish' that clogs everything.
Gasoline is also very dangerous to store.
Diesel - Fuel oil will remain stable for up to 5 years with an additive to prevent wax formation. Propane - An ideal fuel. Propane in a bottle gas tank will store practically indefinetly. Natural Gas - Basically the same as Propane but has even lower available energy. Often you can get connected to local gas mains and have a near infinite supply.