In Eteliria, changing one's main profession, or rather shifting the direction of experience investment, is not unfamiliar to many Invokers. This could happen for various reasons—some lack experience, some might acquire a powerful item that doesn't suit their initial profession's investment direction, or simply out of whimsy, among other reasons.
However, usually, such scenarios occur with less professional Invokers because the time spent is always spent, and won't be refunded due to your changes. Changing your main profession means previous choices are wasted, although if changes are within the same profession system—like moving from Nightingale to Shadow Dancer, or from Ranger to Crossbow Shooter, some former professional skills and knowledge might still be applicable. But transitioning into a completely new domain from Warrior to Spellcaster or Spellcaster to Thief, most former Skills and Knowledge generally go unused.