1.Hehadbeenstudyingforhoursbeforehisparentsarrivedhome.
2.Bythetimeshewokeup,thesunhadbeenshiningforhours.
3.Theyhadbeenwaitingforthebuswhenitfinallyarrived.
4.Thebabyhadbeencryingforhoursbeforetheywereabletocalmhimdown.
5.Wehadbeenworkingontheprojectalldaybeforewerealizeditwasduetomorrow.
6.Thestudentshadbeenpracticingforweeksbeforethebigperformance.
7.Theyhadbeenplanningthesurprisepartyforweeksbeforethebigreveal.
8.IhadbeensavingupformonthsbeforeIcouldaffordtogoonvacation.
9.Bythetimehefinishedhismeal,therestauranthadbeenclosedforhours.
10.Theteamhadbeentraininghardbeforethechampionshipgame.
11.Shehadbeencleaningthehouseallmorningbeforeherguestsarrived.
12.Thedoghadbeenbarkingforhoursbeforetheneighborfinallycalledtocomplain.
13.Wehadbeenwatchingthemovieforawhilebeforewerealizedwehadseenitbefore.