Setting up Smart DNS on a router can help you save you a lot of time that would otherwise be spent setting it up manually on each device and then making sure your IP stays validated.
If you set up Smart DNS on your router, any device that connects to the network will automatically have Smart DNS. This alone will save you much time, rather than having to manually input the DNS addresses over and over again into each device that you need to.
In order to do this though your router will have to have the option to change DNS addresses in their firmware. Once again DD-WRT is perfect for this sort of thing and work flawlessly. The setup is relatively easy and requires you just to input the Smart DNS address into the relevant fields.