I dont think theres any right or wrong way to do it, its more about what feels comfortable with you and what works with your schedule. In my opinion, 6 hours in your given situation would be perfect. What kind of endurance training are you performing though? I believe I've read studies that indicate long-endurance bout type training is negatively impacted by training in a fasted state.
If you're just hitting sprints and doing HIIT, you should be okay. Just play it by ear and see how you perform, then adjust accordingly.