How long does it take to start sales event?

Any sales event setup process is very straightforward and takes about one minute (depends on listings you want to include/exclude from the event). The actual listings change process takes a little bit more. Typical time for full propagation is 5-10 minutes after sales event start time and directly depends on the number of listings you want to put on sale. 

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Seller Tools helped me to manage my shops holiday sales by automatically updating listings that were posted.