Oh, about 6 months.  Knocked out the first grill on my tractor with a fiesty metal fence post dukeing it out with my FEL.  Cost me $180.00.  4 months later, did it again with a stuburn tree branch stuck in a dirt pile.  This time, it took out my left headlight, also.  Cost me $200.00.  Third time, this summer, was moving some tree branches at a job of clearing a fallen hackberry tree.  (very large one)  Branches were under strain in the ground.  I locked on to them with the bottom of the bucket.  WHAP!!!!  There goes the right side headlight!!!  Have you ever seen a grown 40 year old man do some type of wildman dance in the middle of a yard in broad daylight?  I thought I had taken out the grill for the third time.  Walked  
s l o w l e y to the front side of the tractor and saw it was only the headlight.  I keep reminding myself to get some expanded metal welded on the front bracket of the tractor.  Guess I will do it after the 4 th grill!!