Like any pair of leather footwear, you need to treat the leather if you want the boots to come out of winter looking the way they did going in. Timberland claims the boots are waterproof, and in a way they're right. But when they say “waterproof,” they mean that your foot will stay dry, and that water won't enter the boot—not that the leather is actually going to repel water externally. Unless it's specifically stated, you should expect that a lack of leather treatment will leave your boots looking less appealing.
Most chain shoe stores carry a suede protectant and waterproofer. When applying the protectant balm or spray, make sure to add about two coats, wait about 20 minutes between each application. Using a brush to work in the product should help. Overall, don't be surprised if you see some discoloration—how you deal (or don't deal) with that is up to you. But hey, Timbs are workboots after all. Treating them isn't a requirement. Wearing them with a little age or discoloration isn't really a bad thing.