First of all, shimming a door hinge is almost never anything but a bandaid remedy. In your situation, in a 30 yr old house, the floor has done some "adjusting for age", or settling. This is quite common and not nessasarily anything to be alarmed about. It is much more serious when the house is relatively new! So you have a door which has settled on the hinge side, and caused a reveal on the headjamb to open up. You must jack up the hinge side of the door by first removing the door casing on the hinge side [carefully], and cutting the nails that have been at the shims, then , with a prybar, lift the hingeside of the jamb until the head reveal is even. Then re-shim the jamb and renail, making sure that the door to jamb reveal is even and the right clearance. Then re-install the casing. Whala!!!! Your problem should be fixed. If you encounter any problems with this process, please feel free to e-mail me.