It depends on what you want. It’s well known in the industry that Apple tends to unveil its new devices in September of each year, while Samsung usually sticks to a January release date. So, if you want a new iPhone or Galaxy phone, then those will be the times you’ll see a flurry of deals on new models. You’ll also see a good amount of deals landing around Black Friday, Cyber Monday, and other holidays. If you’re not interested in waiting for the right deal to land in your lap, then you can take the initiative by switching to a new carrier or adding a new line to your plan (to make it a family plan). Since pretty much every company has done away with restrictive contracts, it doesn’t really matter when you switch.