Well, not necessarily. Once certain axiomatic knowledge is firmly in place, some things are givens. For example, I no longer have to convince myself that the world is real or that I exist (not that I ever did have to convince myself of that).
Nor do I have to convince myself of moral knowledge, the knowledge that arises via synderesis. For example, every time I have an opportunity to steal, I don’t have to convince myself that stealing is wrong.
However, in the sense that there are always arguments in which to get involved, it can become a full-time job. I guess we have to pick our arguments somewhat carefully. CAF members will know that this site can take up a LOT more time than people can reasonably give it (especially people who are supposed to be working on dissertations! Not to mention names).
On the other hand, the greatest pleasure in life is thinking (according to Aristotle, who perhaps didn’t get out much). Maybe philosophy isn’t a job, but an element of what a human is supposed to be?