There is no right or wrong answer when it comes to how many times you should email your list per week.
Having said that, you must be emailing your list consistently. If you are not emailing your list consistently, they will start to forget who you are which will lead to distrust.
Therefore, as a general guideline we would encourage you to email your list at least 2-3 times a week as a minimum.
These emails will typically be broadcast emails where you are providing value and promoting something.