you might have seen my comment a few months ago about cracking a window too with hot water, i was using it very hot at the time and had just started using it, it put right off using it again but over time and turning the temp down to a warmish water that still helps clean the windows faster its been spot on however i still cringe when i hear frames creaking etc!, i had the glass replaced sharpish and that one off clean turned into a regular clean as she was so chuffed with not only the clean but also how i got it all sorted and didnt try to run, luckily i had a local guy who supplied and replaced the glass for less than i'd pay for the glass alone.
i paid £25 for a piece about 15 inches across by 10 up!