Question isn't relevant to FIREEs who have no gross income. Some percent of spending might be interesting to know.
We donate way too little, right now.
Only a year and 1/2 into FIRE, and need to see how sustainable it is. Already planning a big bump to donations next year (based on donating a large chunk of the new book contract the wife just signed), and we're planning on leaving all of our funds to charity eventually (no inheritances for children, save the case where one has a medical issue and cannot care for themselves, in which case a trust will be set up to care for them, then the surplus will go to charity after they pass. I'm actively against the idea of "donating" your extra money to your kids instead of much less fortunate people, as I've discussed many other times in other threads).
That doesn't push away the responsibility to help now, so I do want to actively increase our contributions (made donations last week to ACLU, EFF, and Planned Parenthood due to election, for example), but it does help me assuage my guilt a little, that it will all eventually go to charity even if we don't do so as much now.