A good procedure to follow after any major work, such as major engine work or timing chain repair, is to get the car back in for an oil and filter change a month after the work has been done. This can help you to be sure that there are no ongoing issues with the motor. This is important as the vehicle may not have been well serviced to begin with, and this may have been a factor in the initial damage.
After the repair, dirty oil with imperfections and particles suspended in it, remains in the block after oil draining. It is very difficult to drain out all of the oil and as much as 500ml of dirty oil can still remain in the block after draining.
The solution is easy, once the repair has been completed an oil and filter change should be booked after 1000-1500k. Just let your customer know that for maximum longevity and performance of the repair, the car will need to be booked in for an oil change approximately a month after the work is done.
Book this oil change in with your customer when they pick up their car. It is good for you and them and ensures maximum performance out of the replacement parts. Some garages have already implemented this as standard practice but it would be great for all garages to embrace this best practice.