Verizon is once again offering an additional 2GB of data per line when adding or upgrading a device to an XL or larger data bucket. In order to get the free data, which is good for the lifetime of your account, you need to be on Verizon's XL or XXL data buckets. The XL plan comes with 12GB of shareable data, while the XXL bumps it up to 18GB. For each line that you add, or upgrade the hardware on, you can receive an additional 2GB of data on either of these plans.
Verizon allows 10 lines per account, so if all of them upgraded or were new lines you would get a total of 20GB of data free each month, or 240GB per year. This data is shareable, and comes at no cost to you for as long as you have the line with Verizon. Remember, for a limited time Verizon is paying up to $650 per line in switching costs to get you free from your current carrier. Combine that with the free data and you may have a pretty sweet deal on your hands now.