One way to tell if your Shopify store sales are sustainable is to look at your Repeat Sales Percentage.
It measures how much of your total sales are coming from repeat customers. 10% means only 10% of your sales are from repeat customers, 75% means three-quarters.
All of your store's sales are coming from either new customer acquisitions or repeat customers. The higher your Repeat Sales Percentage, the less dependent you are on customer acquisition. A low value means that if your primary acquisition channels have issues, you're going to see a larger hit to your bottom line.
I like to recommend a Repeat Sales Percentage target of 50%, where new and repeat customer spending is equal. That gives you plenty of headroom if sales channels falter.
If you use Repeat Customer Insights, Repeat Sales Percentage is automatically calculated for you. It's also measured per-year, per-quarter, and across different sales channels so you can compare your performance.
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.