I spend a lot of time painting backgrounds , that will be covered up

My friend once told me . The best thing you can do in art is paint something really cool and then cover it up. I do spend a while painting a background and then painting over 80% of it. But I feel like it makes the finished product better. Sometimes I take photos of the under paintings (mostly I don't , but I try to document it more)

Here are some examples.

This is the underpainting (see link for finished product)

http://www.madspiral.com/injt1s093v1hhk7zm7hm54scd7qp5x

Here is an underpainting where I eventually put a city. (see link for completed piece )

http://www.madspiral.com/yt8htn0bkupuelo7fvg4obe2awagxb