This has been written about by Julia Wise at Giving Gladly, and others.

Two relevant considerations are:

• Major self-sacrifice tends to be unsustainable, leading to burnout.
• If an EA makes him or herself miserable, he or she is likely to repel bystanders, reducing other people's interest in being EAs.

Giving What We Can has set donating 10% of one's income as a threshold for membership. There's a historical precedent of this level of giving being sustainable for many people, coming from tithing practices in religion.

As for higher percentages: roughly speaking, it seems that marginal returns diminish very rapidly beyond $100k/year, so that one can give everything beyond that without substantially sacrificing quality of life. There are reasons why more can help: for example, to save extra money on the contingency that one is unemployed, or to be able to take care of many children. But I think that the level of sacrifice involved would be acceptable for many people. If one is living in an area with low cost of living, or doesn't want children, one can often live on a lot less than $100k/year without sacrificing quality of life.