I can honestly say that I am a natural blonde. I was, of course, VERY VERY light...just about white blonde when I was little.....that changed about highschool.....and it got just a tad darker, but not much.
I help it out every now and then, just because I see some gray coming in as well as drabbiness.....but even if I don't "help it out"......it turns VERY light in the summer(sometimes too light) and darkens in the winter. I probably can go every 6 months or so for coloring....