The half live of the enanthate ester is around 10-11 days. So you could technically shoot once a week however toward the end of the week your levels will be dropping a little. That doesn't mean you won't see results though.
Best would be to shoot twice a week, but shooting every 5 days would be fine because it is still half of the half-life, so only a quarter of the test will be gone by the time you shoot again. Less shots means less scar tissue so I'm all for that. But really its up to you.