hello @ddschteinn! thanks for your support and comment, her house was stucco to begin with which is actually a decent surface for tile. Anything that is concrete-based is good. Anything that expands and contracts with moisture and temperature (plywood for example) is particularly NOT good for tile :-). Just imagine how the tile stays still while the wood moves. Pretty soon the thinset and grout will flake and crumble and tile will pop off.

I agree that each step winds up being important in the big picture and it's always hard to know at the time which experiences are the important ones. I guess this is why it's so essential to be as present as we can throughout every moment of our lives from mundane to spectacular!