I'm essentially a lazy cook so I make three times the amount of sauce to use it several times. The first day, I make spaghetti alla bolognese. The second day, I make a dish called "pasticcio di pasta" (available on this site) with the sauce that can be eaten for two days.
You can prepare the sauce the day before using it. It will be more flavourful. Add the fresh tomatoes the day you will use the sauce, always 30 minutes before the end of the cooking time.