Just go with the flow. Try to get at least 5 - 6 hours of quality sleep every day and see what happens. If you're fine, then that's all there is to it. 8 hours is a rule of thumb that doesn't apply to every individual out there. Everyone sleeps different hours at different ages, in different places and so on.
If you are sleeping less than what you need, your body will make you rest for a few hours once in a while, to restore the balance. So no need to over-analyze it or try and force your body into more or less sleep, by making the arbitrary 8 hour number the goal to stick to.