In my experience, the people who are frequently sleep deprived for a few years don't seem to be worse for it afterward. My main sources of anecdote for this ar

In my experience, the people who are frequently sleep deprived for a few years don't seem to be worse for it afterward. My main sources of anecdote for this are grad school students with hectic school and advisor setups (who often are partly sleep deprived for much of 3+ years), and parents who have several children in short succession (ensuring their sleep is ruined for roughly 2 years). In neither case do those groups seem to suffer significant long-term effects that are obviously from the sleep deprivation.