The master links that have a plate with 2 pins and another plate that snaps on do not work well when reused. The snap on plate has lips that snap on the pins and hold it in place. Each time you snap the plate on or off the lips wear down. Eventually the lips are too small and when the chain is under tension the plate flies off.
The type that sram use on multi speed chains are intended to be reused. Not just to avoid a poor chain tool join when fitting the chain.