I have never been a big fan of growth limitation by-laws that make a very small number of building permits available. Especially egregious are ones that make a small number available just once a year. Generally, the result is a small number of builders being able to obtain the right to build within a community.
The Eliot example, while providing for 20% of the permits for affordable housing, still limits growth to less than half a percent. And, limits affordable housing creation to about a tenth of a percent of total housing. While moratoria may be necessary for short periods of time, long term building limits, as are typical in New Hampshire and Maine, serve little real purpose.
Growth limitations tend to drive up home prices and make communities more exclusionary.