I get this regularly with large format porcelain. I always lay the tiles flat and show the customer if they bow and tell them how it is likely to look on the wall. Whether I supply or not I take pics and draft a letter to the client confirming my reservations is they decide to go ahead with brick bond. It covers all aspects so there is no worries of comeback later.
As for them coming back 7 months later, I believe the period has to be classed as reasonable. 7 months isn't reasonable in my opinion but then I'm just a tiler 🙂
The best advice for laying any large format tiles, is to put two of the tiles flat on the floor, one on top of the other and facing each other. Then try and spin the top tile!
I always inform the customer of the problems with large porcelain when they want brickbond, the majority I have laid have had a bow in them, this is down to the temperatures they are fired to.
one of their family is supposed to have commented , and obviously they for got to tell them that they had several chances to stop work change layout and even change the tiles all of which was suggested by us !!
showed customer bowing with the side of spirt level just two rows in to job explained effect that this would create suggested normal bond but customer still wanted us to carry on as instructed on brick effect what more can u do other than what customer excepts and agrees ?