I'm going to take a logistical tack and explain why, even though technically rules-legal, it should not be possible for game reasons in most cases, at least for a PC.

##Case 1, PC in a Standard Gaming Group (3-5 players)

This is an ultimate case of "split the party". On character is separated from the there by the gulf of millennia of time. The DM has the choice of whether to run the game for the wizard or for the rest of the party, and must perforce create an entirely new campaign for the future player to play in. This would not be fun for anyone.


##Case 2, PC in a Solo Campaign.

Here there are no other players to worry about, but the DM must still create a brand new campaign. The player character however is now rootless, and anything they might have been motivated to accomplish is now either moot, or lost under centuries of time. Why would Ramses II, thrown through time, care about the rustlers who are plaguing the town of Red Rock in the American Old West? There's a cultural disconnect.

No reasonable DM would allow this, since it requires an incredible expenditure of work on their part, merely to satisfy a single player's sense of self-self-aggrandizement. 


##Case 3, NPC, starting now.

Assuming he starts his program of self-improvement in-game, the outcome should never be an issue. No campaign is likely to last the 3,000 years necessary for it to ever be an issue. In essence, all that has happened is that the campaign has lost a character. He might as well have died for all the impact he will have on any conceivable event.

##Case 4, NPC who started 3,000 years ago.

Congratulation, you have the Big Bad of your campaign. (If you made him the Big Good. there would hardly be any reason for the PCs to exist, hence Big Bad by default). This is really the only scenario where this becomes anything more than a thought exercise. Take note, that even though he has incredible Ability scores, and is a high level caster, he is not omnipotent. A wizard still only has one action and a finite number of hit points. A sufficiently high level party should still be able to reduce him to rubble in most cases.


*Note that I didn't bother including "PC who started 3,000 years ago", because that would be pure cheese.*