Due to reasons still debated by the physics community because of the lack of methods to observe clusters, Rydberg matter is highly stable against disintegration by emission of radiation; the characteristic lifetime of a cluster at n = 12 is 25 seconds. Reasons given include the lack of overlap between excited and ground states, the forbidding of transitions between them and exchange-correlation effects hindering emission through necessitating tunnelling that causes a long delay in excitation decay. Excitation plays a role in determining lifetimes, with a higher excitation giving a longer lifetime; n = 80 gives a lifetime comparable to the age of the Universe.