If you have draught beer or cocktails in your bar the extended closure time means leaving water in the lines (as is traditional) is not a good idea.
The problem with leaving water in your lines, according to the folk at cellar management company Avani Solutions, is that it can result in water taint. This can not only lead to an eggy aroma but more worryingly can, over time, permanently taint the lines and potentially lead to the lines needing replacing. A cost no-one needs.
Avani Solutions have come up with a handy video which shows you exactly what you need to do to Air Clean your lines to avoid this.
If you have postmix then guides have been produced on what to do there by Britvic and Coca-Cola as well.