I’ll jump in here:
I’ve been taking modafinil on and off for 7 years now. I do it strictly for work performance, I do not need it and do not have it prescribed.
I limit my use to 2-3 times/week, 100mg, taken around 5-5:30 AM.
It’s wildly helpful for me to remain alert and focused at work.
It’s worth mentioning that I often combine it with some nootropics of other kinds, I’m very much your Silicon Valley biohacking type when it comes to mental performance (I help engineer and sell significant cloud computing deals, AI/ML, that sort of stuff).
I find it entirely non-habit forming and have dropped it for weeks, even months at a time during slower periods when I’m not working a big deal or intense project.