Why do you care about reactivating lapsed buyers?
Because they are worth more than new buyers.
In this example the new buyer spends $111 in the year acquired.
The reactivated buyer spends anywhere between $123 and $132 in the year reactivated. In other words, the reactivated buyer is likely to be worth 10% to 20% more.
This also means you can spend more to reactivate a customer than you can spend to acquire a new customers (because the customer will pay you back faster) ... and marketers love that kind of stuff.
Your cheapest, most direct, and most effective tool to reactivate a customer is email marketing.
Your best indicator of a lapsed buyer ready to reactivate is a website visit in the past 1-4 weeks.
Go get those lapsed buyers ... convert them ... at least get them to your website, ok?