You’ve got it. The aspects you get from completing dungeons you unlock forever, but the stat rolls are the lowest they can be. The aspects you extract from an item match the stat on that item, but are one time use. So for example, if the aspect can give +10-20% Damage to x skill, the dungeon perma-unlock will always give you the 10%, and the aspect you extract from an item will give you exactly what was on the item. So what you typically do is look for “max rolled” aspects and extract those.