Everyone places a different value on their time. Some may do RV transport just for a little extra cash and a way to pass the time, without a real concern of running their truck in to the ground or needing to "make a living" doing it.
Others might find that their time is more valuable, and that they need a job that will pay the bills such as a house and vehicle payment,and transporting RVs may not cover it - unless you run the max time allowed - but then you will likely burn yourself out being gone so much.
There's a point when you cross the line and a job is no longer enjoyable, and the money paid isn't worth what it takes to get that money. and what's the point in making money and just being able to pay the bills and nothing more?