Adwords campaigns should follow an “always on” approach as this ensures there is never a situation when a customer is searching for your business and you are not present, i.e. capturing full impression share.
There may be situations in which you need or want to switch off your Adwords PPC advertising. For example, bad publicity, budget cuts, ecommerce system down, national holiday etc.
Pausing Adwords for any length of time can have an adverse effect on quality score. This is because during the period for which an account is offline, competitors remain live, gathering CTR etc and improving QS. When an account is paused, its QS pauses whilst competitors QS continue.
However if you choose to pause an account, then the best way is to set the budget end date to end or to pause all campaigns.