Australian Civil Aviation Order 20.6 gives guidance to the continuation of flight post an engine failure.
3.2 The pilot in command of a multi-engine aircraft in which 1 engine fails or its rotation is stopped, may proceed to an aerodrome of his or her selection instead of the nearest suitable aerodrome if, upon consideration of all relevant factors, he or she deems such action to be safe and operationally acceptable. Relevant factors must include the following:
(a) nature of the malfunctioning and the possible mechanical difficulties which may be encountered if the flight is continued;
(aa) the nature and extent of any city, town or populous area over which the aircraft is likely to fly;
(b) availability of the inoperative engine to be used;
(c) altitude, aircraft weight, and usable fuel at the time of engine stoppage;
(d) distance to be flown coupled with the performance availability should another engine fail;
(e) relative characteristics of aerodromes available for landing;
(f) weather conditions en route and at possible landing points;
(g) air traffic congestion;
(h) type of terrain, including whether the flight is likely to be over water;
(i) familiarity of the pilot with the aerodrome to be used.
"d" above could be quite restrictive if in a twin engined aircraft.