we've just kept a spare in the fridge. just add some of your last batch of kombucha to a plastic ziplock bag with the spare scoby and set it in the fridge. It will last a month or so in there. By that time if youre continuously brewing, you'll have a new spare to replace it with. We end up with more scobys than we know what to do with, so having a spare on hand has never been an issue.
As for starting a new scoby, you should be able to cut a piece of one to use without a problem. We get a new one about every 2 batches we do, which is about once a month.