The longer the better, so long as you keep topping it up. My mum makes the worlds best xmas pud. She once used fruit mixture that had been soaked in alcohol for 3 years! When cooked it was as black as charcoal and you could only have a sliver it was that rich.

Her secret is to soak the fruit in big tupperware containers. They get turned regularly and another bottle of booze added to keep the fruit moist. You dont want the fruit drying and crystallising. She usually mixes the fruit for xmas in march.

Can you tell I'm a little bit enthusiastic about my mum's xmas pud?