Google and Facebook have helped build a lot of successful businesses.

They can be highly measurable, relatively easy to start, scalable and exceptionally good at reaching people when they're interested in buying.

So when should a business do something else?

There isn’t a spend level at which you suddenly “graduate” from search and social.

But there is a point at which it becomes sensible to ask whether continuing to put every additional dollar into the same channels remains the best way to grow.

$20,000 a month is $240,000 a year

A business investing $20,000 every month in marketing is making a $240,000 annual investment.

That doesn't mean it should immediately start buying television or outdoor advertising. Search and social may still be exactly where that money should go.

But at that level of investment, it's reasonable to ask a broader question than whether the individual campaigns are performing:

Is the way we're allocating this investment still appropriate for the next stage of growth?

There are some useful signals to watch.

Are additional dollars producing additional customers? Is acquisition becoming progressively more expensive as spending increases? Are you increasingly reaching people who already know the business? Are you struggling to reach genuinely new potential customers? Is the business growing at the rate the marketing reports suggest it should?

If the answers start changing, the media mix may eventually need to change too.

Broadening the mix doesn't mean abandoning what works

Adding another form of advertising doesn't require turning off paid search or Facebook.

Different activities can perform different jobs.

Search might continue capturing people already looking for what you sell, while video introduces the business to people earlier. Social might help generate consideration while streaming television creates broader awareness.

The right architecture depends on the problem.

And sometimes, after looking at the evidence, the answer really is:

Keep doing what you're doing. You're not ready to broaden the mix yet.

That's a perfectly good marketing decision.