The average civil war was 10 years as of 2002
Civil wars are longer and bloodier than average when foreign powers intervene: A 2008 study by Fearon and David Laitin reaffirmed previous research stating that civil wars tend to be significantly longer when foreign countries intervene decisively on one side. (To be clear, "intervene" here means more than just training a few rebels, as the United States is doing, but to support one faction in outright defeating its enemy.) A 2012 paper reached a similar conclusion, also finding that foreign interventions tends to make all sides more violent and to increase the death toll. Iran is very actively involved in directly aiding Syrian President Bashar al-Assad's forces, as is the Lebanese militant group Hezbollah. Saudi Arabia and other Arab Gulf states are helping to fund and arm rebel groups; foreign jihadist groups are also involved in the fighting, particularly from Iraq.(4) Civil wars with lots of factions last longer than average. Barbara F. Walter of the University of California at San Diego points to a 2006 paper in the Journal of Political Science arguing that civil wars last longer when there are more competing factions. The number of rebel groups tends to change on a pretty regular basis, but Walter says there are 13. Whatever your count, there are a lot of them, their alliances and allegiances tend to change a lot and, most worrying,they're already fighting one another.