Yeah, i typically boil for 60-90min and get around 12% boiloff. Usually ~1gal per hour. I was working with a 5.1gal MLT at this time, so i made up for that with the addition of the DME and corn sugar, as well as the longer boil. The sugar helped to dry it out down to 1.013, i believe.
You don't need a monstrous boil - just enough to turn over the liquid in the kettle and to vaporize such things as DMS precursors, etc.
~~ Malted barley wants to become beer. ~~