come back, it wont be much fun. The whole point is where you stop along the way. Hana is a tiny little town with little of note, but the journey there is full of more awesome stuff then you can get to in one day. The key is to down load the gypsy road to hana app. It uses the GPS in your phone to tell you exactly where to go and where to stop. This is vital because it is not developed and clearly marked. Some of the coolest things are nearly impossible to find if you are just reading a description of how to get there. Whereas the app will tell you "after you cross this next bridge park on the left side of the road, there you will find a hole in the fence..."
We found one place that had incredible cliff diving that I will never forget. It is also great because it helps you know what is worth stopping at and what isn't. It will tell you for example, that if it is before x am, you can stop at this place, if it is after x am, you probably don't want to stop.
Anyway, the road to hana is a must do. Bring cash and get the app. It will take all day, but it's a blast.