The only time I ever use gradients is when I'm doing a Color - Transparent. Most of the time I just create layer after layer and add new gradients while changing the blending mode to get the desired effect.
The only time I've ever saved a gradient is when I've made custom metals.
Base on my more or less 4 years experience in using PS. I haven't tried to save gradient, there is an option that you can load all default gradient style.