Empires however are a costly affair to maintain if the subdue regions do not accept the situation. Morocco's occupation of Western Sahara only has produced one net gain - nationalism and national unity in Morocco proper, aiding the fairly corrupt Rabat government to divert attention from a general failure in its own development policies. The Moroccan settlements in Sahara, established to secure the legitimacy of territorial claims, are on government subsidies, not to mention the military effort in securing claims. These costs will never be paid by the relative rich fishery resources off the Sahrawi coast nor by the scarce dessert resources, which only the Sahrawi people have the competence to exploit efficiently if granted peace and auto-determination. Resources, both natural and human, are not exploited but rather systematically destroyed.
Military costs are extremely high.
But the opposite forces are gaining momentum. National unity in the DRC may very well be re-imposed on short term, but to make it lasting will be a close to impossible task. Sudan can never become a united, peaceful country under Khartoum's control again. Khartoum may win decisive battles in the future, but a stable and durable situation cannot be found until the map has been redrawn - be it a Sudanese Confederation or two separate states. The question is rather, how many more years of blood spilling does Southern Sudan have to endure before there is a will to negotiate in Khartoum.