I'd like to think my work will last until the customer gets bored of it not because they have to change it because it's coming up. The thing that gets me is that you keep advising fixing methods that no one has ever recommended! Why would you make up your own
rules? If you can find me any written document anywhere where it recommends fixing to 6mm ply or indeed using the cow pat fixing method, I'll take it all back. Simply saying that you've always done it like that and never had a problem, really doesn't wash, for all you know, your customers tiling has failed and they don't want you back in their home to rectify it. I get a lot of recommendation and repeat work, so I'm fortunate enough to get to see work I've done several years ago and guess what, it's all ok and further more, it wasn't fitted with cow pats over ply wood.