I do not drop mine below 60, many of my friends do without any issies. I actually did not start cooling my rosys until a couple of years ago, and produced many nice litters. however, I worked mainly with coastal's at the time and now only keep desert localities.
-----
Keeper/Breeder of
Sand, Rosy, and Rubber Boa's, Drymachron, Alterna, Black Milks, Thayeri, and Crotalids.