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.
Optimize your promotion timing to save money and attention
Repeat Customer Insights will analyze a ton of customer behavior data for you, including their buying cycles.
If you knew exactly when the majority of your customers were ready to buy again, you can increase your orders and profit just by tweaking your message timing.