Colonies can, and frequently do, fail over the Winter months. If one has more than one hive there is a better chance of survival through until the Spring. The surviving colony can then be split to found new colonies once they have built up their numbers on the Spring nectar and pollen.
Over the past few weeks I have been considering the purchase of another hive. Realistically I am unlikely to get another colony this year* but it will be ready for the start of next year and its components are alway useful to have around.**
Over the weekend I bit the bullet and hit the purchase button on a Supplier's website. At about ten o'clock this morning I received two very large boxes containing a flat pack hive. These are now sat in the hall and over the next week or so it looks like I will be assembling another hive.
---* There is an old saying;
A swarm of bees in May is worth a load of hay
A swarm of bees in June is worth a silver spoon
A swarm of bees in July isn't worth a fly
Basically if a swarm arrives in July it is really too late in the beekeeping season for them to build a sufficiently robust colony with adequate stores to survive the Winter.
By the time I get my new hive built and sited it will probably be way too late if it attracts a swarm and certainly too late for a nucleus colony.
** Spare Supers are always handy to have around to give a strong colony more space for nectar stores.