How long can you leave flux on before soldering?

Could you elaborate on the duration for which flux can be left on a surface prior to soldering? Is there a specific time frame that should be observed to ensure optimal soldering results? Does the type of flux or the material being soldered impact this duration? Are there any risks associated with leaving flux on for too long, such as corrosion or damage to the soldering surface? Understanding the recommended timeframe for flux application would help ensure the quality and durability of the soldered connection.