Ammonia has been considered as a potential atmospheric biosignature on rocky planets with atmospheres primarily composed of nitrogen and hydrogen, dubbed “Cold Haber Worlds”. Previous research suggests that enough ammonia could be produced on these planets to be detectable from Earth, but these efforts have not quantified their long-term habitability. Here, we analyze climate model simulations of such atmospheres, including their composition and surface temperatures, and discuss questions related to the lifetime of high-hydrogen atmospheres.