How long will it take to heal after a broken femur?

Depends on severity. A lot of variables come into play with this answer. Did you need surgery? If you needed surgery, did the surgeon have to use hardware to fix the fracture? Do you have osteoporosis? If the fracture is bad enough, it may take upwards of 6 months to heal and for the patient to be back to normal activities (this is including physical therapy).
I agree but. . . . Femur is the largest and strongest bones in the body. Other than the femoral head at the hip, the blood supply is pretty good. If well stabilized (the most common treatment for a femoral shaft fracture in an adult is intramedullary nailing), in some cases it may be nearly healed in 6-8 weeks. Some surgeons will allow you to bear wt on the implant even before this. But this isn't the whole story.