Some editors work with lots of video layers with clips overlapping each other, with some clips disabled as reference and so on. But once the rough cut has been approved, you should clean everything up so that there isn’t anything on your timeline that isn’t necessary. I recommend copying your approved master sequence and doing a cleanup job that includes the following:

• Bring down any clips on upper video layers into making one or two video tracks. The exception would be if you were using multiple layers for the purpose of showing parts of them at once as a composite.
• Discard any reference clips or alternate scenes that are no longer relevant.
• Do the same with audio clips.
• Insert bars/tone/slate countdown prior to the beginning of the program. Change the timecode start time on the sequence so that, with the bars/tone/slate/countdown included, the timecode hits 1:00:00:00 at exactly the first frame of the program. Be sure to designate the timecode format as drop frame or non-drop frame as per the delivery specs. My standard setup on this is to establish the sequence start time as 00:58:50:00, edit in one minute of bars/tone, then the slate/countdown, the 2-pop at exactly 00:59:58:00, and program beginning at 1:00:00:00.
• If you are preparing a combo sequence for more than one spot or program, start the second spot at exactly 00:00 of a subsequent minute. For example, :30 spot one starts at 1:00:00:00, spot two starts at 1:02:00:00, spot three at 1:04:00:00, etc.