the biggest problem i have found when running high Ca is that it can build up on warm objects in the system. pumps and heaters. it can build up so much that it can melt pumps when the motor seizes. submersible pumps are notorious for this.
really high alk and Ca are not more is better. just keep it stable and at normal levels and all will be good. this is one of those things were trying to hard can lead to bigger problems later.