Understanding the limits to AR spatial 'memory'

The whole point of AR is being able to 'place' virtual 2 or 3d objects so that they appear to 'stick' in the real world. But what are the limits to this 'stickiness'? Is it related to time ( elapsed after when they were placed), distance, or something else entirely like the amount of device movement after placing an object (since the internal device gyroscope plays a role in calculations)?

Let's take an extremely hypothetical example. You climb Mount Everest, launch your AR application and place a virtual flag at a specific spot at the very peak. Without ever closing your application, you descend and a year later again climb to the summit. Will your virtual flag still be there in the same spot?