How much advertising is enough? Well, what are your objectives? If your objectives are to build brand awareness, then there is never quite enough because more advertising increases brand awareness.
However, it has to be the right message. Consider your audience and repeat the message until it needs changed. The important factor in any b2b advertising campaign is frequency. A minimum of every other month is essential to build and maintain brand awareness to any audience.
Even if your products have a very limited audience and you feel that you know who they all are, a regular reminder that you want their business will help.
Enough advertising is the amount needed to get the job done.