It's a good question.
One of my tanks ia 72g with the same light setup as yours. I run 2 bulbs 8-9 hrs and I run full strength (4 bulbs) for about 3 hrs. At startup 2 bulbs around 6 hrs and 4 bulbs around 1.5 hrs. Until I build up to the 8-9 hrs.
The range of lighting, etc in planted aquaria is quite wide, it usually comes down to what kind of setup you have and your lifestyle (how much regular maintenace you want to do), but generally speaking less light 'duration' at startup especially has always meant less algae issues to deal with.