As a LEGO ambassador, I have not only contacted TLG about cracked torsos, arms, legs (back side of foot), headlight bricks, 1x1, 1x2, 2x2, 1x1 cheese, I have given bags of broken elements to CEE reps over the past 5 years. My cracked LEGO seems to be mostly torsos and arms. Mostly from the 90's and newer from small sets including impulse and polybags. Large sets with minifigs are fine. Temps, lighting, and humidity in my house are normal. Also note there is very little direct sunlight. My 90's minifigs were all fine until a few years ago. The cracking in my house seems to be a discouraging epidemic. I'll also note that I have been working with TLG regarding the yellowing issues of light bley and whites. I've done studies on retrobrite and everything no go.
I think after a while TLG turns a deaf ear to us. We probably complain far more, 1 being adults and having the access and time to do it, 2 we purchase on average far more than their target market does so we would have more broken parts then the general population.
Here are a fwe examples and I'm sure we all know the age of the figs. My LEGO are built for display, events with my LUG, and stored built together between shows.