The Flex 3401 is a beast, that's how I sign my how-to book because it's true. It will take a beating and keep on buffing and when it doesn't it's usually for good reasons, like constant use or the wrong gauge extension cord etc.
For the volume of work you do Jeff you should really have two of these machine anyways.
At my last class I stressed this and in the future I'll stress it in all the classes that if you're a full time detailer and use the Flex 3401 you should have two of these tools for these reasons,
1. If one breaks or needs servicing you already have a back up so you don't lose work or customers.
2. Have one set-up with the factory 5.5" backing plate and one set-up with the LC 4" backing plate so you can use the tool that is best suited for the panel you're buffing out without having to stop and change backing plates.
3. If you have helper then they can be just as efficient as you.
Also, the lower the number the heavier duty the cord. For running a power tool like the Flex 3401 off an extension cord a 25' 10-gauge cord would be correct.