Even being at the front of the queue it can be difficult to promise that Z% of screenshots will be returned to you within X seconds as a lot of the time required to take the screenshot is dependent not on GrabzIt but on the target website.
So if the target website is hosted on a fast servers, like the BBC or CNN websites then the screenshot will be almost certainly be returned to you within five seconds. Unfortunately if the target website is hosted on slower servers then the delay could be longer. Also if the target website has a lot of heavy content then this will again increase the time it takes to return the screenshot.
Another issue can be caused by creating large screenshots which can take longer to download from our servers.
However we have invested a lot of effort optimizing our system to ensure that we always return screenshots in the quickest time possible time regardless of these issues.