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Letter: How to know when it's the right time to give up

Published 26 November 2025

From James Stone, Buxton, Derbyshire, UK

We can learn much about when to give up from the natural world. When a bee is collecting pollen, there is an optimal time to give up expending increasing amounts of energy, and deliver the pollen to the hive (15 November, p 28).

Charnov’s marginal value theorem states that if there are diminishing returns on effort (which there usually are) then maximising long-term rewards is achieved by quitting when the initially high instantaneous reward rate falls to a point where it equals the long-term reward rate.

The lesson for us is that we should quit struggling with an increasingly unrewarding project when the long-term reward starts to flat-line. This might seem obvious, but what is obvious is not always true, so it is good to have such intuitions confirmed by such a beautiful theorem.

Issue no. 3571 published 29 November 2025

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