I once tried to crystallize a solution of ammonium nitrate by boiling. I boiled it down really far and the temperature kept rising and rising. I thought I would see it crystallize any second but it never did. Finally, the solution turned a pale yellow color and smelled of ammonia. I then realized I was looking at boiling ammonium nitrate! This is quite dangerous as, though rare, pure ammonium nitrate can detonate under extreme conditions. Not wanting to find out exactly how extreme, I removed the heat immediately and left the room until it had cooled down.
A much safer and smarter method would have been to predict stoichiometrically how much product would just dissolve in a volume of solution near boiling point, boil the solution to slightly above that volume, and then remove the vessel to an ice bath or refrigerator to crystallize quickly. In general, attempting to crystallize any compound from a boiling solution can lead to unwanted decomposition and other undesirable results. For evaporation crystallizations, I find keeping continuous air flow over the solution with a fan greatly increases rate of drying without the need for heat.
Hope this helps!