Throughout the country only a few places require that new affordable housing projects agree to maintain that affordability in perpetuity – Boston is one of them. CEDAC’s Bill Brauner is quoted in Coalition For Smarter Growth’s article advocating that DC follow Boston’s lead and require very long term affordability restrictions.
http://www.smartergrowth.net/wp-content/uploads/2017/03/LongTermAffordability_FINAL_web.pdf