One objection that I would have that would permit me to allow myself to not need to donate ceaseless entrails of currency to foreign aid companies post-empirical-research and thereby maximise the moral output of my spending, would be that there is additional moral value to aiding one's own community in favour of that of others. That said however, that is only going to be a continuum. You know? Saving 1 life in my community still cannot possibly be morally superior to saving... 1000 elsewhere. But it's a start.
Next I could add in other reasons to refrain from absolute altruism (if I may call it such) even as a utilitarian so as to bring about the most developed society and cause the most human social/economic development in the long run. Such as, if you do have a certain level of excess you do have the right, as that is your property, to consume it without any feelings of moral guilt. This however is again a continuum. And there would be two factors which would influence whether that means you have to give away any of your money or not.
Firstly, obviously, how much excess you actually have. If you have great excess, you still need to give some away. Secondly however, I think it's important in a society to reward hard work and innovation. A lot of jobs are quite menial, they can be quite monotonous and they don't pay greatly. But if that is you performing at your own personal peak then you should be allowed to enjoy a greater proportion of that income without feeling moral guilt from not having donated to others to aid them with your excess - this is because feeling guilt in such a scenario isn't really conducive to a great society. I feel that would, in the long run, lead to societies full of selfish people, the mentally ill, the un-cooperative and generally just an inferior society.
Clearly, societal development for my ethics is key. I think I can from that perspective, that is, one of a more welfare utilitarian sort of approach, defend my not donating significant chunks of my excess income to others. However, I do think that Singer's argument does follow through for anybody that would happen to have a very similar theory of normative ethics to himself, that is, some basic form of consequential utilitarianism that is heavily heavily focused on the outcomes in terms of people's actions, states of being or people's preferences being achieved.
Nice couple of posts above though. Appreciate that.