Jammedstab, it will depend on the airline / aircraft and airport. Most paper AFM charts have a maximum distance for distant obstacles of 72,000 feet, and as someone else has pointed out the Type A chart may go out to about 10 miles. So the airline back engineering guys will look at the airport, decide if 10 miles is enough, if not they will take the obstacles out to the maximum that they can by obtaining topographical maps for the airport and surrounding area. If in the event that the obstacles are further than 72,000 feet, they will be scaled down so that they can be used in the AFM chart.
Ideally, all engine failure procedures should have a finish point, some say this should be the MSA, but unfortunately for most aircraft the software doesn't exist to calculate this, so its best to take the aircraft to a fixed point and hold.
The newer digital AFM's allow for further distances to be calculated and with the advances in Google Earth and the fact that collecting terrain data has become a lot easier. the results should be better procedures.
The process isnt always perfect, there was a positing on here a few years ago where someone wrote about an engine failure procedure from a Greek island, the procedure turned out over the sea, but they completely forgot about the next island!
Mutt