If a fruit cake has been fully iced it will be sealed to the board by the marzipan and icing and will keep for a couple of months before the icing starts to discolour. Do not store in a sealed container, but keep it in a cardboard box (cake boxes can be purchased from cake decorating suppliers and are not expensive) and store in a cool dry cupboard.
Keeping the cake for several months – If you want to keep the top tier of your wedding cake until christmas or your first anniversary, store in the same way as above. However as the icing will have become discoloured and the flavour deteriorated, you will need to completely strip the cake of the icing a marzipan and recover it with fresh.
Once the cake has been cut, it will start to dry out because the marzipan and icing seal has been broken. It is then necessary to store the cake in a sealed container and eaten within a month as the icing and marzipan will start to go soft.
If you find that the cake is forgotten or that it hangs around (especially after Christmas), try cutting it into portion size pieces and wrapping in cling film.
I have found that by putting these ready to eat pieces in a tub in the kitchen, they disappear quite quickly as they are handy to pop into a lunch box or are a ready snack for when hungry teenagers/partners arrive home. They also have the advantage or being more nutritious than a packet of crisps. I also find a piece of fruit cake goes down very nicely with my mid morning cup of tea on a cold dreary winters day.