You should wash/moisturize morning and night.
Think of it this way; when you are sleeping your skin is most active. It's rejuvenating itself. You are also breathing on your pillow, your hair is on your pillow and let's face, possibly even drooling on your pillow. Your face is on your pillow.
I have one cleanser for night to take all the make up off and a gentle one for the morning.
Moisture both morning and night. You should have a daytime moisturizer with an SPF of at least 15. This will protect you against sunlight and indoor lighting as well as the pollutants in the air.
There are very light moisturizers out there if you feel your skin doesn't need so much, but, your skin does need that drink of water morning and night!
Since we live in Colorado our elevation puts us that much closer to the sun and it's so important!