Depends on the drop rate of the item in question. If I feel I can get it in only a few runs I will keep going until the parts show up for me. If it is a terrible drop rate I take what I can get and go.
"... if you let the fly live, the spider is going to die. You can't save both without one suffering.." - Knives (Trigun)
if its a quest reward like the sandhawk or rubi i will dashboard till i get what im looking for since usually its worth it. however if its like a CC or Bee I will take whatever drops since the drop rates are super random