For my G30, I loaded the mags full and left them that way for a couple fo days. Now I can fill them by hand, but the thumbs DO get sore after a few reloads. It's much easier using the loading tool.
Leaving the mags full will NOT harm the springs.
Never had a problem with the mags not dropping out. Sounds like somethings not right there; a full mag is pretty heavy and should fall right out.