I came to the same conclusion after taking modafinil daily for 5 months. I quit because I was getting completely drained by 7pm. I had to hit the bed as soon as I got home, and then slept for 10-12 hours straight. I did the arithmetic and it wasn't worth it. Supposedly, there isn't such thing as a "modafinil withdrawal," but I was nonfunctional for about 6 weeks after I left it cold turkey. Not only that, but because I wasn't aware there was a withdrawal phase, I thought my symptoms (not being able to wake up, narcolepsy, nausea) were an ominous sign of an underlying disease.

Taking modafinil daily, especially for that amount of time was not a wise move. It's a uniquely "safe" substance but even the most avowed users stress not to take it daily even if for nothing more to preserve perceived effectiveness.

Yikes, are the effects still lingering? Have you returned to baseline energy/focus?

That was four years ago, and I was back to my baseline self in about two months.

A month ago I was diagnosed with severe apnea, and since starting treatment I feel like a different person. I wonder whether the apnea was worsened by modafinil four years ago, and that was the reason for my constant wearing down. Maybe I'll do an experiment just to see, but I don't need stimulants anymore to be productive, not even coffee.

Isn't modafinil/stims a treatment for apnea?

I believe you're thinking of narcolepsy