One question I hear often is when should a store stop marketing to lukewarm customers.
In Repeat Customer Insights I'd recommend using the advice in the automatic segments. It's recommendations will include recommendations to not market, for example in some of the defected customer segments.
But if you don't have the app, you can still make some rules of thumb based on how you answer these questions. Just be ready to adjust these every now and then as your business evolves.
How expensive is the marketing? If it's free or cheap (e.g. email marketing) then it might be worth continuing. Make sure to include your discounts you offer as marketing expenses.
Have long are your buying cycles? If customers buy every month normally, going six months without an order is odd and can show a defected customer.
How much does seasonality impact your orders? There might be customers who only buy during holidays or give your product as regular gifts.
Do you have the ability to easily segment and stop marketing to groups? If it takes hours each time to figure out who to stop contacting, it might be easier to just market to them and put your time into something else.
How reliable is your activity tracking? Tracking email opens is notoriously unreliable but tracking actual orders works well.
The easy answer of when to stop marketing is when it's no longer profitable. But figuring that out on your own takes time.
Measure which customers you're retaining and which you're losing
In order to keep your best customers, you need visibility into what's going on with them. Repeat Customer Insights will help you track down where you're losing customers and how to better target new ones.