One of the requirements of the law of returns is that all factors except the one under consideration remain constant. No doubt Crusoe could maintain his high rate of productivity by spreading his coconut-gathering efforts over a long period of time—perhaps working only one hour at a time, then waiting a few months for the most accessible palm trees to regenerate their bounty. The law of returns would not be applicable in such a context, however, since additional supply of a vital land factor (namely, the unharvested coconuts) is constantly provided. (Regarding the scope of application of principles, cf. pp. 3.4:4-6.) At any given point in time, however, the law of returns poses a practical limit to Crusoe's ability to satiate his desire for coconuts by allocating more hours of labor.