The way I look at it, when a magician summons a particular type of spirit, she gathers all of the magical energy that resonates with that spirit type from the surrounding environment, and gives it form and expression. The spirit reflects the tradition and beliefs of the summoner, and in some respects her personality and expectations as well. In one sense, the summoner creates the spirit on the spot. But in another sense, the spirit was always there, sleeping, waiting to be called.
If the same magician summons the same type of spirit in the same place, she'll get the same result. The spirit will respond to the same name, will look and act the same way, and will appear to remember the summoner and whatever happened the last time it was called. But if she summons a different type of spirit in that place, or the same type of spirit somewhere else, the result will be different. If another magician summons the same type of spirit in that place, the result will be different.
Every spirit is a unique mix of the qualities of the summoner, the place, and the spirit type.
At our gaming table, once you summon Clearsight (a Force 4 Spirit of Man) in your apartment, then Clearsight will answer every time you summon a Spirit of Man in your apartment. Once you decide it has the Analyze Device optional power, it always has that power. If you feed it more juice next time (Force 6), it can have a second optional power. But if you summon a Spirit of Man somewhere else, it won't be Clearsight (unless you Summoned and Bound the spirit at your apartment and brought it with you). You're free to define a new set of optional powers.
None of this is official/canon; it's just the way we play it.
