Guys.
Divine Creation uses the Greater Create Object formula, but merely allows for magic items instead of just mundane.
You can get Greater Create Object to have no rest period for the creation up to 300gp.
Using this ability is a full-round without a rest period.
There are magic items worth less than 300gp.
Pun-Pun has copies of himself that he can give items to.
Pun-Pun has Arcane Generosity.
Pun-Pun has NI Full-round actions.
1) Full-round action, create Feather Token.
2) Readied standard action (move?), give token to Copy-Pun, gain 6XP
3) repeat steps 1&2 twenty-one million times all at once, become level 500, advancing every base class up, advance every PrC.
Since this is all happening at once, due to NI full-round actions and NI readied actions, this can actually be any level desired.
Pun-Pun has NI XP. Thus NI class levels. And can increase them to a NI extent as an Immediate Action with Celerity + Time Stop + Greater Celerity + etc. + etc. + etc. + et alli.
There is no way to gain True Infinite XP.
Any method of gaining XP would have to be defined in order to be awarded, you cannot hit infinite in any defined way.
The ways in which Pun-Pun hits TI for things is because of manipulating areas that are undefined.
XP has to be, must be, defined in order to be awarded, or else it cannot be awarded.
Infinite CL?
Only nigh infinite, so it won't kill a truly infinite amount of enemies.
An additional problem with killing infinite creatures is that you're too high ECL for them to grant any experience points. If you instead treat everything as a single encounter, modifying the CR accordingly, you will be too low ECL to gain any experience, or you will only gain one non-infinite sum.
This is my supporting point. CR =< ECL-6 or CR=> ECL+6 has no defined XP, thus you cannot say that you do gain it.
Even though the DMG basically states that the DM would have to Ad Hoc it in order to award it. But if you went with that, then:
A) It would be based on difficulty of being overcome. Pun-Pun had no difficulty = no XP.
B) If DM wanted to award, then the encounter must be quantified to be figured. Then would be figured. Then XP would be awarded.