According to Nigella you should transfer it to an airtight container and it will freeze for up to 3 months. Defrost overnight in the fridge. It may separate if so whisk or give the container a good shake.
You could turn it into dulce de leche. In Argentina last year I had some croissants at breakfast that had a large dollop of dulce de leche stuffed underneath the top flap (and then sprinked with icing sugar). I`m not a sweet pastry lover at all but they were divine. You could have a bash making those.