The conversion would stop according to the chemical equation when 33.7 g paracetamol is added to the 20g sodium hydroxide used to make 250ml,but in practice a bit less paracetamol since the hydrolysis solution has to be strongly alkaline.The sodium hydroxide is used up and converted to sodium aminophenolate.
Nobody has ever done what Sreenath suggested - fine tune the amount of sodium hydroxide- so his original estimate has more or less got chiselled in stone as PaRodinal.