Service records may help you identify a sensible time to check in with a customer. An upcoming maintenance date or agreement renewal is a more useful starting point than a general sales blast.
Separate a reminder from a prediction
Equipment age and past service can suggest a conversation. They do not prove the equipment is about to fail. Predicting a fault from monitoring data is a different task that needs suitable equipment, reliable readings and qualified review.
Check the records
Confirm what was installed, what was recommended and whether the service is already booked. Make sure the customer can appropriately be contacted.
Offer a clear choice
Explain the maintenance or plan accurately, including what is covered and what is not. Whether customers take it up depends on their needs and the offer.
Would it be easy to find the customers with a genuine service milestone approaching in your current system?