I have applied for 70 since finishing my Masters mid-October. I am also currently doing a paid part-time role too. It is an extremely tedious process but I've got to the point now where I've done so many competency phone/video interviews and so many psychometrics that I've seen/prepared for every question and done every format of test. I now find them extremely easily. Similarly, I've done so many AC's in the past 2 months that I am 100% calm before and during the day; a stark contrast to my first when I was literally shaking with nerves before my presentation.
As with anything, practice makes perfect. I've not necessarily got through to so many ACs, and received some offers because I will be the best person for the job, but through sheer volume and repetition of the processes. Although as another poster mentioned, spreading yourself this thin is a risk, particularly if there are ones you really want. This is because application processes vary greatly depending on the company, some (for example the financial sector) require lots of technical knowledge. Whereas others (for example Boeing) didn't ask a single technical question, or have any exercise that made use of any research I had done, it was entirely self-contained.