Or worded differently: once i establish longer-lasting facts through narrative or 'create an advantage', are they aspects beyond the scene? If PC finds an item, for example, or some character aspect should change in the light of the narrative because it is no longer true. If something about the character is established in the narrative, should it be part of that characters aspects?
The short answer is yes. It is because of the Bronze Rule i.e. the Fate Fractal on Page 270 of the Fate Core rulebook.
The trick is to describe the elements you are dealing with in natural terms first. Look for logical subgroups or subelements. For example Super Porsche, a car with super tech, can be described as a character in its own right. In addition the Super Porsche's amazing engine can also be its own character.
Now you ask about aspects specifically. I like to think of aspects as packages. A package in a generic system (Fate, GURPS, Hero, Savage World) a bundle of traits (attributes, advantages, flaws, gifts, skills, etc) that describe an element of the setting. A campaign revolving around Navy Seals would have different packages for the different MOSs.
Now aspects in fate are natural language descriptions of some element in the setting. A Navy SEAL demolition specialist would have a demolition specialist aspect with benefits and limitations. A Super Porsche Amazing Engine would have an aspect of requiring Unobtainum as a fuel source with own attendant set of complications. The fact that a characters is from New York's Hell Kitchen can be an aspect with benefits and complications.
Remember per the Fate Core rules on page 56 an aspect is
Unique or noteworthy is why you don't need to list every attribute or bit of information about a thing or character as an aspect. Only the things that are important to the campaign should be made aspects.
It becomes part of the character when it's more important than the other aspects that they have. Something as ephemeral as the Create Advantage action probably won't change a character in such a fundamental way, and (probably) neither will getting an item.
Hmm. Example time:
We've got a character with a couple of aspects: "Always stand up against bullies" "Fight smarter, not harder" "I'd be super if I wasn't a little guy."
Some stuff happens, and you wind up in the army, and you get a cool prize if you get the flag from the top of the pole. No way your Mediocre (at best!) Athletics is going to Overcome the Great difficulty to get you up there, but you're smart so you use Notice to Create An Advantage to put the Aspect of "The pole is held up by a single pin". This allows you narrative permission to use Mechanics (or Notice, or something else) to Overcome, or maybe the difficulty goes down (or you just spend the free invoke or whatever). This aspect doesn't stick around, because it's no longer important to the story.
Later on, you get stuck in a machine, and collect a piece of equipment called "Super Soldier Serum". In addition to moving some of your skills around (and getting some stunts, and generally going from being a 92 pound skinny guy with bad lungs to a Super Soldier) you drop that "I'd be Super if I wasn't a little guy" for "Dr Erskine's Greatest Invention".
Also, in the Cap vein, things like his .45, or the various guns he picks up? They're stuff that gives him narrative permission to use combat (or just fluff in the description of the combat roll) The shield, on the other hand, could be described with an Aspect ("Shielded Super Soldier")