For what length of time can someone survive with primary bone cancer with no treatment?

Depends on a number : Of factors: 1: whether the bone affected is an extremity (arm or leg) or the torso (trunk). The extremity ones are probably DX earlier; 2: the extr. Lesion could be treated with removal to get rid off it, or by amputation; 3: patients general condition, whether he/she will be able to stand the chemo or radiation; 4: cancer type, some are slow growing; 5: time of diagnosis.

Depends: If it is an aggressive bone cancer like osteosarcoma or ewing sarcoma than it is unlikely that someone would survive more than a year without treatment.