It's really the sugar in a rich fruit cake that preserves it, lasts fine without alcohol if there is enough dried fruit in it. Light fruit cakes won't last as well and neither will low sugar or no sugar versions. Alchohol mainly for flavour especially in the baking part. Some argument possibly for brushing the outside of a fruit cake before storage with alcohol to sterilise the surface but will last a long time without it too. The poking of holes and dribbling in alcohol during the 'feeding' period is purely flavour and moisture and realistically unless you're sterilising the poking instrument every time you're just adding a route in for bacteria but not much lives in the high sugar environment of a fruit cake! I've kept fruit cakes for up to a couple of years just wrapped in a cool dark place, our modern overheated homes are not friends to the sort of storage of these cakes that was typical in days gone by, under the bed on a cold floor was classic place but with underfloor heating etc it's a guarantee of spoilage these days!