Utilitarianism is almost certainly much more demanding than Mill allows. It is tempting to think, in fact, that Mill is deliberately being disingenuous here. He was quite aware of how much further there was to go before customary morality became ideal, and that the route to that ideal would seem demanding to many. The rhetoric to encourage people on that road comes in chapter 3 of Utilitarianism, especially in the closing paragraphs. Here, he may be more concerned to allay doubts. Better to persuade a reader to become a feeble utilitarian than put them off entirely by stressing the demandingness of utilitarian morality.
Roger Crisp, Routledge Philosophy Guidebook to Mill on Utilitarianism, London, 1997, p. 115
Since, according to maximizing utilitarianism, any act that fails to maximize is wrong, there appears to be no place for actions that are morally admirable but not required, and agents will often be required to perform acts of great self-sacrifice. This gives rise to the common charge that maximizing utilitarianism is too demanding. […] How should a utilitarian respond to this line of criticism? One perfectly respectable response is simply to deny the claims at the heart of it. We might insist that morality really is very demanding, in precisely the way utilitarianism says it is. But doesn’t this fly in the face of common sense? Well, perhaps it does, but so what? Until relatively recently, moral “common sense” viewed women as having an inferior moral status to men, and some racs as having an inferior status to others. These judgments were not restricted to the philosophically unsophisticated. Such illustrious philosophers as Aristotle and Hume accepted positions of this nature. Many utilitarians (myself included) believe that the interests of sentient non-human animals should be given equal consideration in moral decisions with the interests of humans. This claims certainly conflicts with the “common sense” of many (probably most) humans, and many (perhaps most) philosophers. It should not, on that account alone, be rejected.
Alastair Norcross, ‘The Scalar Approach to Utilitarianism’, in Henry R. West (ed.), The Blackwell Guide to Mill’s Utilitarianism, Malden, Massachusetts, 2006, p. 218
The objection that consequentialism demands too much is accepted uncritically by almost all of us; most moral philosophers introduce permission to perform nonoptimal acts without even a word in its defend. But the mere fact that our intuitions support some moral feature hardly constitutes in itself adequate philosophical justification. If we are to go beyond mere intuition mongering, we must search for deeper foundations. We must display the reasons for limiting the requirement to pursue the good.
Shelly Kagan, ‘Does Consequentialism Demand Too Much?’, Philosophy and Public Affairs, vol. 13, no. 3 (1984), p. 239
[T]he demands of morality pervade every aspect and moment of our lives—and we all fail to meet is standards. [F]ew of us believe the claim, and that none of us live I accordance with it. It strikes us as outrageously extreme in its demands[.] The claim is deeply counterintuitive. But it is true.
Shelly Kagan, The Limits of Morality, Oxford, 1989, p. 2
Sometimes I feel that the moral life is so close now, I can almost touch it.
Zell Kravinsky, ‘I Feel Better for Giving Everything—Whether My Money or My Organs’, The Daily Telegraph, August 8, 2004
It is by no means inconceivable that the special character of our art and our personal relationships depends upon the cognitive biases and limits that prevent us handling philosophical problems, so that philosophical aptitude would deprive our lives of much of their point. Philosophy might require even more self-sacrifice than has traditionally been conceded.
Colin McGinn, Problems in Philosophy: The Limits of Inquiry, Cambridge, Massachusetts, 1993, p. 156
Saying that something involves excessive sacrifice implies that you already know what the right answer is: it makes sense to speak of giving something up only against the background of some standard. But if you already have the standard (for example, that each person has a “natural right” to whatever he can make in the market) then the criticism to be made of other criteria should be that they happen to be incompatible with it. Nothing is added to this by talking about the “sacrifice” called for by utilitarian or other criteria.
Brian Barry, Theories of Justice, Berkeley, 1989, pp. 82-83
Professional philosophers […] have been more interested in using the issue of famine relief as a club with which to beat utilitarianism over the head for its allegedly extreme demandingness than they have been in upholding the moral necessity of doing far more than most of us do now to aid those in distress—or in exploring why our culture is resistant to that message.
William Shaw, Contemporary Ethics: Taking Account of Utilitarianism, Cambridge, Massachusetts, 1999, p. 287