If your spheres are getting dirty or dusty, just take a hose to them! They are made out of recycled plastic, so a bit (or a lot) of water won't harm them at all. If they have any larger debris like branches or leaves, just remove those first.
Just let the snow melt off naturally! When it gets very cold, the plastic can become a bit brittle. This is no problem under normal conditions, but vigorous brushing may damage some of the leaves. Leaving the snow on the spheres won't do any damage at all!
Too much exposure to bright sunlight can cause some minor fading over the course of the several years. If you have several spheres, try rotating them out! This has the added benefit of changing up the look of your garden as well as increasing the lifespan of your spheres.
Long answer: Due to their immense size, we ship our spheres in two halves to help reduce your shipping costs as much as possible. When you receive them, you'll just have to use a pair of pliers to pinch them together, then give them a little fluff with your fingers, and you're all set!