If you want to believe what is being said in DC, they have been closing in since '07. KSM gave the name of a courier in early 2007. It took the CIA about 2 years to locate and start tracking this courier. It took another 18 months for the courier to lead the CIA back to this compound.
I dont know how much OBL had to do with day to day ops at this point, but as a symbol, he was every bit as important as the man that is calling the shots.