I got to 1,000 photos a lot faster than I'd thought. The good thing about digital photography is that you can take all the photos you want and not waste film. The bad thring is that you have to go through all those photos and decide which ones you want to keep. When I go on a vacation, I average about 300 photos, only a small percentage of which are keepers. They all go into Photostream, though both the photos I take with my iPhone, and the photos I import into Aperture with my point-and-shoot Canon Powershot. Since I always have my iPhone with me, I often take pictures when I'm out for a walk or on a day trip. Then there are the "strictly for information" photos for example, when I was doing renovations on our home, I took lots of pictures of products at Home Depot and such so I could compare, research, and evaluate them later. None of these were meant to be keepers, but they went to Photostream nonetheless.
To be on the safe side, I'm going to continue manually syncing my iPhone with my Mac and importing my photos into Aperture. Unfortunately, there's no good way to test my question. If I intentionally avoid syncing my iPhone, and photos that automatically are deleted from Photostream also are deleted from Aperture, then those photos will be gone for good. I suppose I could shoot 1,000 non-keeper test photos and see what happens to them, but it's easier to sync.