I used fresh猪腳 after 出水 (about 20 min). I will put it into the freezer. I would take the necessary amount into a pot with some old 薑醋 1 or 2 days in advance before serve.
Very important is I will cook the 薑醋 separately. That is to take some old 薑醋 to cook with the 猪腳 instead of using all the old 薑醋 to cook. You could also add some new 醋 if you are cooking with the 猪腳. You could make it sour or sweet by adding different of new 醋.
Sorry I don't know how to type in Chinese and hope you understand what I mean.