Google ads should be used and available as part of your overall marketing strategy. They can be set up and switched on and off as and when required and useful for all sorts of scenarios:
Launching a new product or service
Introducing your business to a new sector or geographic location
Boosting an area of the business where interest has waned
A completely new business
A healthy mix of SEO efforts and a sensible Google Advertising Campaign is we think a recommended position to be in.