I leave about 1-2 inches of lead in the bottom of my 10 lb LEE pot and it takes about 10-15 minutes (on 7 or 8 ) to liquefy the lead.
These pots are very nice, 100 times safer, and 100 times faster than the old way I used to do it.... heat pot of lead, usually weighing 10 lbs or so, and try and pour into the mold without spilling/overfilling and burning the crap out of myself.