[capt jgwinks]

Right about documenting your sea service. USCG requires 360 days for inland and 720 days for near coastal. If they required that all to be documented paid time on commercial boats none of us could ever get licensed. I hold a 200 ton master ticket and have taught the license courses for about 15 years. We always tell the students that the sea time just has to look possible and the CG will accept it. You only have to document that you owned the boat(s) for a length of time that would make the time you are claiming look possible. There is no way to document whether you actually ran the boat that much or not. I've never heard of them asking to see your logs or anything, but I suppose they could if they didn't believe you.
The tests are not an indicator of ability either, especially the Navrules exam. It's all about how well you memorized the wording in the book as opposed to how you would run the boat.
But, if you want to get paid, you need the license, so you jump through the hoops anyway.
You can get the license without taking a course (I did it), but it's extremely difficult. To pass the exams you need to know the exact wording of the rules, not necessarily the meaning of the rules. A course will teach you how to pass the exams.

 

[capt jgwinks]

An online course is another way to go if that learning method works for you. The courses are self paced and you have six months to complete. You have to pass online quizzes along the way so you should have a good idea whether you can pass the real exams at the end. I proctor the live exams for one of the schools and I find that the average scores are much higher than those of my class room courses. I have no idea how many students start the course but never finish though. I suspect it's a large percentage. The classroom courses pretty much guarantee passage. They give you whatever personal attention necessary and most will let you run through it again until you pass.