From an engineering point, I'm sure that the code that returns that string simply examines your current experience value, instead of your entire experience history
might a check on current xp value and number of posts be a closer approximation to xp history without sacrificing (much) performance?
i don't know much about what goes on here behind the scenes, but i can't imagine this solution would cause a noticable performance degradation. i would argue, however, that this is an edge case, and i'm sure there are more important issues which affect the experience of a larger number of users--there would be little gain from this change.
~Particle *accelerates*