I haven't experienced any warping. They get very little to no direct sunlight, and the house is maintained pretty close in temp and humidity year round. There's everything from some very old catalin, pearl and service stocks, to Ropers and Sandersons, and the southern Cali guys Farrant and Stark. Spegel, Fishpaw and Herretts (a few Cloyce too) are probably the newest. And there are some unidentified in there as well. Very few factory grips in my collection, I'm really only interested in the older custom pieces.
Now I know I would want to see more! Your speaking my language! I collect mostly custom myself but if something factory with great wood grain or wood type shows up I might step up.
You have a great collection of grips.