This type of work is good where it can be had. I worked 12 TA positions during my 40 months at McGill. I was also a fully funded PhD student for three years.
My PhD was a job, one that I did exceptionally well, just as I do all my jobs exceptionally well. When you do well at a job you are rewarded, and I was rewarded. I got the PhD.
Be careful of getting too attached to TA and RA work. The problem with treating work in grad school like a job is that it fundamentally is not a job. It is school.
Work and funding in grad school can create dependencies, especially if they drag on too long. I got so used to getting TA jobs, polishing them off in short order, and then getting more TA jobs as a result, that I came to take TA work for granted.
The problem is, once you graduate, you go to the bottom of the list. The irony of course is that by doing an exceptional job, by finishing early and in timely fashion and exceptionally well, you make your own livelihood obsolete.
Then, out of grad school and into the mean machine of the world, you are forced to adapt like never before. There is nothing wrong with this, but I came to realize how sheltered and protected grad school was.
The longer you wait around in grad school, the harder it is going to be to get out into the real world. I do believe in this real world, as a world that is fundamentally different from grad school, and from academia in general. Academia is a protected and special place.
My advice then is go into grad school with your eyes wide open. Have an exit strategy in place from day one.
GradLife McGill 