We evaluate the effects of a fundamental lever of constitutional design: the duration of public office terms. We present a simple model grounded in interviews with legislators and highlight three forces shaping incentives to exert legislative effort. We exploit two natural experiments in the Argentine Congress (where term lengths were assigned randomly) to ascertain which forces are empirically dominant. Results for separate measures as well as an aggregate index of legislative effort show that longer terms increase effort. Shorter terms appear to discourage effort not due to campaign distractions but due to an investment payback logic: when effort yields returns over multiple periods, longer terms yield a higher chance of capturing those returns. A broader implication is that job stability may promote effort despite making individuals less accountable. Copyright 2011, Oxford University Press.