gwern is partly right about my motivations.
I have some sort of sleep disorder (perhaps narcolepsy; the sleep study I had was inconclusive on that, though it did rule out sleep apnea) where the treatment might involve taking stimulants. My sleep quality at night might be particularly bad in general, and taking a stimulant could make it worse. Modafinil's half-life is about 15 hours, which is quite long. Even if I took it in the morning, it still might impact my sleep at night.
Also, the stimulants I have had generally do not agree well with me. Often they make me nervous, even in low doses.
If I were to take a stimulant regularly, I'd rather take a short-acting one, and only take it when absolutely necessary.
I have some armodafinil now and am going to do a study on myself. My sleep doctor suggests testing my concerns as they may not pan out in reality.
I'm under the impression that taking substances in intense spikes generally causes tolerance to occur more quickly than taking a slow build-up and slow come-down dose. The former profile is also superior for avoiding negative high/crash side effects resulting from rapid ramp-up / come-down.
However, the only actual sources I can find for which this is true relate to insulin, which could easily be a special case, and I'm not really sure where I got this impression. It's filed away in my mind's "conventional wisdom" drawer and I've never questioned it until today. Can anyone who actually knows confirm/deny this?
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.