Simplify getDuration() & fix @return docblocks
Simplify getDuration() & fix @return docblocks

fabfuel/prophiler,zhangjingpu/prophiler,fabfuel/prophiler,lajosbencz/prophiler,lajosbencz/prophiler,zhangjingpu/prophiler,lajosbencz/prophiler,zhangjingpu/prophiler,fabfuel/prophiler,zhangjingpu/prophiler,zhangjingpu/prophiler,lajosbencz/prophiler,fabfuel/prophiler,lajosbencz/prophiler