Automated workflows can really help you engage customers who haven't interacted with your business in a while, securing inactive subscribers back . But it's important to strike a balance when it comes to customer contact. People have busy lives, and no one likes to be disturbed. But it makes sense to set a period of inactivity, and to make this something that encourages them to send a message to their email address. The standard seems to be around a couple of months.
It’s a good idea to offer rewards when you connect with customers. A discount or special offer or a brand new product. A friendly, encouraging message that shows you value your customers and miss their traditions is also a winner.

Of course, some customers will opt out of your email list, and it's worth encouraging them to come back without rushing them. Often, companies resort to sending re-engagement emails to customers who have opted out, effectively giving them a fresh start and enticing them to start the customer lifecycle all over again.
The example below from Amazon's audiobook platform Audible illustrates the types of offers that might bring back lapsed customers. The audiobooks offered here can be tailored to a customer's tastes, making them more appealing.