Think of it this way.
If it's down to the customer, they will want it repairing. If you're their tiler, you could be for life, so charge them for it and do the job, it's just another paying job, what's the cause of the job matter for? ...but explain throwing a wobbler because the milk ran out and slamming the fridge door which knocked the big spuds saucepan on the damn ceramics isn't "workmanship related".
You guarantee fixtures, fittings and workmanship. Not the products, they're guaranteed by the manufacturer (adhesives, grouts) but not the tiles, no tile gets replaced at the cost of the factory.
Topps Tiles do a buy-back service and take a small loss overall on the tiles that come back and are not the current shade and can't be sold on. But they gain when a customer breaks a tile as now they come back to the shop to see if they have the tiles still, they don't, they sold them off in job-lots, and now the customer's looking around the shop floor again for a whole new load.
Whatever the cause of the fault, providing you've done a good job, you'll gain out of going back to your customers. you will find the odd door strip has just been ran over a few times with the kids toy Quad, just tell them to buy a new strip and you'll stick it on when you're next passing. You might find the customer has slammed the door and a whole corners worth of grout has cracked, tell them pay for the grout and you'll pop by one day and do it.
Don't bend over backwards but never loose your customers.
It's just business.
