Is it always necessary to change the brine in the pot-stewed vegetables?

You don't have to change it. You can burn it in the morning and evening in summer and once a day in winter. Take good care of it so that it won't break when you get old. My friend barbecued in a hotel. Yes, when I was a chef, I was assigned to the halogen room at first. Our bittern is also burned in the morning and evening in summer and once a day in winter. Remember not to move after boiling. If you move, it will burn. Only amateurs would say to put preservatives. Salt water will not deteriorate if it is properly preserved for hundreds of years. It is said that some old bittern is still used in Qing dynasty, when the bittern barrel was too big and it was too troublesome to put it in the freezer. We have never let go of the freezer for years, let alone put any preservatives. The food produced by Lao Lu is really delicious.