I don't think is coincidence that it's common to, "lose interest in character's role-play" at about that time, it seems to me more likely that they are simply bored because they are hardly leveling anymore. I'm not a mathematical stat person, but I notice that the exp. required to increase level is very incremental, (X^(2) every ten levels, perhaps more?)
Another possible explanation for this phenomenon,(if you can call it that) is that primary skills are maxing out about this time. Example: one handed, light amour, restoration, archery and conjuration.
I'm currently playing a Breton spell-sword with said skills, and even with the mage stone, the warrior skills maxed first, namely, archery. Restoration was last long after even conjuration. (Even despite of the fact that the former is leveled by amount of points healed which dramatically rises at higher levels)
What I'm trying to say here is that the dramatic nature of exponential increments coupled with skill maxing may account for this, "freeze" as I mentioned earlier. Some experienced opinions would be appreciated along with some hard stats.