Dyn recommends using an update client on one of your computers, rather than your router.
In general, we have found the software clients in computers to be much
more reliable compared to some router update clients. The reason for
this is there are varying degrees of support for DynDNS in routers and
While these devices may claim to have DynDNS support, they sometimes
are very buggy or not properly using our update API. This can cause
issues such as abusive updates or maybe the update client not even
being able to send us an update consistently. Abusive updates are the
flooding our update servers with the same IP address every minute or
so instead of only sending us an update when the IP address changes.
Software update clients are available for Windows, Mac OS X and Linux, so you should be able to squeeze one in just about anywhere.
In practice, having used Comcast Business for five years now without a static IP address, the IP address has changed only twice. The first time was immediately after an extended midday outage caused by a cable cut (~2 hours). The second was after moving to a new location. In each case I just updated my DynDNS records manually. (Your ISP may vary dramatically.)
I recommend you contact your ISP and get a static IPv4 address if this is a serious cause for concern. You should also consider obtaining an IPv6 allocation; these will be provided statically. A /56 should be sufficient for a small office environment.