Donor-advised funds do reap a significant cost advantage (foundations carry a 2.5-4% of assets overhead expense to maintain, a 1-2% excise tax on NET investment earnings and a required 5% spending of assets each year) but may also have one more drawback: a limited lifetime, although this varies depending on the sponsor. American Endowment Foundation for example allows successor advisors in perpetuity. While a foundation can persist for generations or in perpetuity, some sponsoring organizations impose a "sunset" on donor-advised funds, after which they collapse individual funds into their general charity pool.