I've had mine for nine years. It covers ANY waterway anywhere. I could go guide saltwater with it if I wanted to.
As far as renewal, no, you do not have to retest for five year renewal, but as noted, provide lots of documentation of sea service, medical, etc. It's a hassle, but not nearly as much hassle as obtaining it originally.
Lots of Tennessee guides "run under the radar" without their USCG. TWRA doesn't really care and I've been told directly they won't check for it... although they'll definitely check for your state guide license. However the USCG enforcement folks make periodic, albeit rare, visits to different bodies of water and definitely DO enforce it if you happen to get checked.
They came to the Chattanooga area last summer and spent at least four or five weeks on Chickamauga and Nickajack lakes. I personally know of one guide who got nailed, although he did receive a formal, written warning.
There are six of us who guide under the "Scenic City Fishing Charters" umbrella. Four of the six now hold their USCG 6-pack. The other two have completed all requirements and testing and have submitted their applications. Sadly, the USCG indicates they built up a huge backlog of applications during the government shutdown. It's unclear how long it's going to take for those applications to get through the system. Normally it takes the standard government "4 to 6 weeks." We fear it might take longer right now. :bash: But once the red tape gets cut, Scenic City Fishing Charters will have six USCG-licensed guides. I'm proud of that.