I also just wash my fabric as it comes in the house. It is just one more load of laundry. If I have a fabric I think will run I will test it to see how much bleeding there will be. Then I know if I should do that separately with a fixative. If some fabrics bleed a little, a normal wash usually takes care of it.
By the way, I have never had a fabric ruin a quilt project because of bleeding. Is there a lesson here???????
peace