When you can no longer provide additional value to the tax dollar, that is cannot add more necessary roads and bridges (or repair the ones we have), cannot remove more people from homelessness or poverty, cannot make people any more likely to be economically productive (which is the root for healthcare, unemployment insurance, pensions, Social Security, Medicare, Medicaid, etc) or add any more real security or safety (as opposed to the false “security” of the TSA), that is when going further would be too much.