Do you mean charging and updating them? I’d do that as soon as you get them. It took a couple of hours to charge mine when I first got it, and after the first charge it needs to download and install updates. Once it’s all set up, you can turn it off. I plan to turn mine back on about a week before our trip to make sure it’s charged and ready to go.
ETA - I assume you mean the MB+, which has a rechargeable battery. The MB2 don’t need charging or updating and are ready to go immediately.