The town was small, remote and short-lived: growth stalled before 1332 and in 1383 it was recorded as having only 10 residents. Davies comments that its location, accompanying a castle site chosen for defensiveness and ability to radiate strategic power, undermined its economic viability: "the artificiality of [its] commercial setting was too obvious once the military opportunities... had been removed". The economic weakness of Cefnllys is also emphasised by historians Oliver Creighton and Robert Higham. Major outbreaks of bubonic plague across Britain in 1349, 1361–62 and 1369 contributed to its failure, and the persistent threat of violent conflict within the March expedited its demise. Cefnllys remained a borough after the decline of the medieval settlement, and according to the 1831 census it comprised, besides the church and castle ruins, 16 inhabitants in "three Farm Houses and one small Cottage".