Too often, keepers feel they need to get right up to the ball before diving for it on a breakaway. The problem is, this makes the timing extremely difficult because the keeper does not want to dive when the ball is at the attackers feet (if they dive when the ball is at the attackers feet, the attacker can simply touch the ball to the side and beat the keeper) yet the attacker is not going to get so close to the keeper as to allow the keeper to just fall on the ball.
The alternative is to be willing to attack the ball as opposed to falling on the ball.
Rather than trying to get within a yard or two of the attacker and then waiting for the long touch, look to take the touch when the attacker is 10 yards from you (just an example). The way to figure out how far you can actually take off from is to experiment in training. There is no set distance that will always work for all keepers and the distance will be effected by the speed of the oncoming player, your speed and explosiveness, where you are in the penalty box, the surface (a wet surface will allow you to slide further which can be both good and bad) and many other factors. While there is not a set place a keeper should take off from, it's a safe bet that you or your keepers are taking off to close to the ball and have to be willing to explode to attack the ball once you see the bad touch.
The alternative is to be willing to attack the ball as opposed to falling on the ball.
Rather than trying to get within a yard or two of the attacker and then waiting for the long touch, look to take the touch when the attacker is 10 yards from you (just an example). The way to figure out how far you can actually take off from is to experiment in training. There is no set distance that will always work for all keepers and the distance will be effected by the speed of the oncoming player, your speed and explosiveness, where you are in the penalty box, the surface (a wet surface will allow you to slide further which can be both good and bad) and many other factors. While there is not a set place a keeper should take off from, it's a safe bet that you or your keepers are taking off to close to the ball and have to be willing to explode to attack the ball once you see the bad touch.