Good point. It seems there's no "free lunch"--the body will maintain equilibrium (for example, see caffeine or alcohol consumption).
The "no free lunch" model is a good one. I have found that cutting out other activities like watching television and limiting the amount of on-line game playing gave me more time, focus, and energy for work. Thinking about what you can give up or defer to get what you want should be part of any calculation around stimulants to reduce your need for sleep. I still drink a lot of very strong tea (because, for me, the side effects were fewer and less burdensome than coffee) but I don't try and get less than six hours of sleep and know that if I cut it to less than four a price will be paid, if not the next day within two to three days.
It would, however, be interesting to momentarily feel what it's like to obtain that kind of concentration in order to try to mimic it without the drug.