First of all, most bowlers should try to end within a foot of the foul line. Your ball will not roll properly if it touches the approach before it gets on the lane. Also, most oiling machines don't get oil on the first 6 inches of the lane either, so you want to avoid that too.
If you are letting go of the ball before you want to, it is a matter of figuring out why. Most common reason is the thumb hole being too big. Most bowlers will use thumb tape when the hole is too big, and take it back out as your thumb swells. If this isn't the issue, it may be that the angle/pitch of your thumbhole needs to be changed to allow you to grip the ball better. If you have a pro shop at the bowling center you bowl at, have the operator watch you throw it and he will help you out if it is something you are doing yourself, or fix it if it is the balls fault. Hope this helps!
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