Let me try to explain what the other person is saying. If you have an 8gb spacer file, at some point the disk will get full and cause some errors, so you will

Let me try to explain what the other person is saying. If you have an 8gb spacer file, at some point the disk will get full and cause some errors, so you will have to log in, remove the spacer file and then deal with the problem. If you have an alarm for 8gb remaining, you will receive the alarm before any application ever notices the disk is full. You will have basically the same amount of time to solve the problem for good, but if you're able to solve it before these 8gb also ends, you won't have to deal with any "app crashed/misbehaved because it reached a point where no space was available" issues.