Most people report FE and HP gains by advancing the timing by a few degrees. This tells me the factory uses conservative timing advance to be on the safe side.
Location plays a big role in this. I live at a mile above sea level and pretty much anything on the road can get a boost in power and economy by advancing timing. The Durango is limited to 40 degrees of advance and it does 40 quite often. The drag strip is open for test n tune this weekend and I plan on going there to test changes in timing and some other stuff.