unfortunately for me... I was changing wiper blades and the arm slipped out of my hand 6 inches and crack!! now the hunt is on for a fix or all out replacement ...ugh!!!

 

I got a small (tiny) rock chip down in the lower "black" just above where the driver side wiper arm sits.... a crack about 4" long started to form up the windshield but still below the normal "line of sight". I was able to get a glass company to do a "stop drill" at the end of the crack and then fill that hole and the crack with their chip repair stuff. The insurance paid 100% of the repair and the crack has indeed stopped growing. A lot less expensive than my $500 deductible "comprehensive" insurance for a replacement windshield! We'll see if it survives the extreme temperatures of winter...if not then it'll be a replacement.

 

I don't know if there is a brittleness that develops with age, but I've had previous vehicles for many years with no windscreen issues, and this past month my 2013 ES300h has been hit by 2 small stones, that pitted the windscreen and then on Friday something that looked to be 1-2 inches in diameter flew across the freeway divide and hit the lower drivers side windscreen creating a pit and radial cracks about 1.5", during the rest of the drive home, one of those cracks grew to extend across to the passenger side of the windscreen. No choice but to replace it. Like many posters here, I believe it comes down to luck how your windscreen deals with small stones. Not sure anything else would have dealt any better with the large object this past Friday though.