I was thinking about replacing the existing shower with a walk in. I have done a bit of research regarding the base. I see some plastic/acrylic/cast iron pans...36 x 60. Like the look of tile on the floor but the critic in me thinks what will that floor look like in 20 years, grout will be all dirty. So thought about an plastic/acrylic/cast iron pan then tile the walls. Thoughts and opinions?