Sorcerer changing spells

[Crexis]

As a sorcerer, it states that I can change one spell for each level that I have. So at some point,I can change a level 1 or 2 etc spell for another one.

I assume you can change this when you gain a level, but can I change spells at any level? Is there a limit on how long I have to change a level 1 spell?

I assume I can change a spell at any time but I'm unsure.

[Kitty Catoblepas]

prd wrote:

Upon reaching 4th level, and at every even-numbered sorcerer level after that (6th, 8th, and so on), a sorcerer can choose to learn a new spell in place of one she already knows. In effect, the sorcerer loses the old spell in exchange for the new one. The new spell's level must be the same as that of the spell being exchanged. A sorcerer may swap only a single spell at any given level, and must choose whether or not to swap the spell at the same time that she gains new spells known for the level.

At every even level, presumably when you level up. The limit seems to be that it's only one per even level 4 and after (9 total).

[Dasrak]

Sorcerer wrote:

Upon reaching 4th level, and at every even-numbered sorcerer level after that (6th, 8th, and so on), a sorcerer can choose to learn a new spell in place of one she already knows. In effect, the sorcerer loses the old spell in exchange for the new one. The new spell's level must be the same as that of the spell being exchanged. A sorcerer may swap only a single spell at any given level, and must choose whether or not to swap the spell at the same time that she gains new spells known for the level.

Right there in the class description.

There's also the retraining rules, which don't require you to have leveled up, but do require the expenditure of time and money.