This is not a question of how much gold you have. Rather how much gold do you believe you need for expenses to become moot.
I myself picture 58-68k being an ideal amount for myself. The only large expense I have to worry about are BiS crafter epics, and currently they can be quite expensive. I don't really fancy ultra-high-end vanity items such as old TCG mounts or that one cooking recipe you see on the AH from time to time that's going for 52k.
How about you?