Hamsters are always trying to have two different escape openings in whatever space they enter. Whether it is a nice looking, store-bought, hamster house, or just a hole in the ground.
This is of course especially important when the hamsters enter a new tunnel/space etc. But, they still do it in the different places where they might have lived for years.
I think you as a consultant should mimic this in your work. But instead of having escape openings in your tunnels, you should have ways of escaping unwanted clients.
You should, of course, do your research and make sure that the clients you are making deals with are the sort of clients you want to work with. But no matter how good research you do, some clients will just start to disrespect you, your time, and your work, and in does situations, it is important to have a way of escaping.
Don’t accept too long contract periods, don’t accept too long termination periods. If you make good and important work, your clients will want to keep you as a consultant, and as long as they value you and act with respect (and pay), you’ll probably want them as a client. You don’t need any longstanding contracts for that.