Seth Godin wrote about the state of DTC advertising and why it always leads to ruin.
His solution is simple, though not easy:
Your (current) customers need to bring you your (new) customers.
Eric Davis
Market to your customer's timing
Figure out how long customers wait in-between purchases and you have a key component for your marketing timing. This is the basis of the Average Latency metric and Order Sequence Report in Repeat Customer Insights.