The SwiftPaws Drive is meant to be used outdoors, but it houses electronic components that can be damaged by rain. While the housing is water resistant, it is not water proof and should definitely be brought inside when it rains.
Protecting the drive and controller from the elements is necessary. If you opt to cover the drive with plastic, you run the risk of water getting in, which will damage electronics. Doing so is of course your option, and you might be willing to take the risk short-term. But we do not recommend it.
It's best to bring the drive and controller inside after each use. Leaving the pulleys out should be fine.
To get the most out of your equipment and investment, please protect it from the elements when not in use.