When Black is komaster he lives with Black 1. Later White 4 - Black 7 is sente.
Now White 1 - 3 makes a 10,000 year ko shape in the corner.
As a rule Black should bite the bullet and make the ko right away. In exchange for the ko he gets to play Black 6 elsewhere. If he waits for White to make the ko he will normally get less in exchange.
kb: Bill, is "Black should play the ko immediately" still true if Black has the ability to play and generate some large ko threats somewhere else - e.g. in order to change komaster status?