It seems to me that the way a task is framed greatly affects how much willpower it requires.
Yes; I can't remember which overcomingbias posts it was in, but Robin Hanson has floated a theory that willpower is a hack whereby, for social reasons, we override our natural and correct (in the EEA) instinct. Obviously, it doesn't pay to make such an ability infinitely strong; people who go on hunger strikes to make a point have few offspring. So, a task framed as something useful in the EEA would require much less willpower than something framed as socially praiseworthy, but otherwise harmful.
I recently read this book. I've tried to summarize the main points below -- you can read my notes here (MSWord doc). You might also find Derek Sivers' notes useful, which can be found here.
NOTE: The general model of willpower (as a finite resource consumed with use) used in this book does not seem to represent a scientific consensus -- see the comments for more detail.
General Claims
Willpower Depletion
Restoring Willpower
Miscellaneous
I declare Crocker's Rules.
[i] I didn’t see enough evidence to conclude whether the cravings are actually stronger, or people are simply less able to resist them, or both. The book claims that both are true.
[ii] The book seems to imply this mental nagging costs willpower, but I don’t recall it being explicitly stated. GTD is also mentioned, and the lack of Next Actions which one has the materials to execute being included in plans causing people to procrastinate. (p. 79)
[iii] The relevant experiment was conducted in a laboratory, so there is no possibility of the experimental results being affected by the fact that people with more self-control may keep their house cleaner. Self-control was measured in ways like being willing/unwilling to week for a larger sum of money instead of receiving a smaller sum immediately, and choosing healthier foods over sugary snacks.
[iv] I wonder if this means that people are more likely to ignore opportunity costs.
[v] ‘Conserving willpower’ is also mentioned around here, which seemed to imply that effective precommitment helped reduce the willpower costs of overcoming constant temptation by making the decision easier.