RECIPE FOR THE BEST DULCE DE LECHE:
Keep an eye on it to make sure the water level stays high. The label will fall off, don't worry. Remove and let cool. It's now done — open it right away or keep it in the pantry, it needn't be refrigerated until it's opened.
Source:
http://spectacularlydelicious.com/2010/04/13/evitas-dulce-de-leche