I say in the range of 450-500 before someone finally can't take anymore grinding.
No grinding necessary, just depends how many times people are willing to flick through the oghma infinium!
Patched my friend.
What it really depends on, is how many times people are going to resto-loop super expensive potions then sell them, leveling alchemy/speech -> 100 in one shot.
I could hit level 500 in about three hours I figure. Probably less, if I bothered including smithing in the loopiness. = )
Seriously. I predict a character of level 'several thousand' before someone actually gets tired of that. It wouldn't even take more than a day or two I figure. --- Remember: IamI3rian told ya. OSG-> Best corp in Dust.