Great idea!
I used to drink a few mugs of coffee a day at work. I could drink half a dozen cups at dinner at a restaurant and fall asleep easily as soon as my head hit the pillow at home. Never had trouble sleeping eight hours, with or without coffee. Ever. Until....
When I hit my 40s (hello, perimenopause!) I found out that caffeine was affecting me in completely different ways than it did when I was younger. Couldn't fall asleep, got heart palpitations. I weaned myself off completely and didn't drink any coffee or tea for maybe 10 years. It helped some but I've never experienced the blissful uninterrupted sleep I did in my youth.
I started to have a cup for breakfast in the morning. No problems cropped up. A cup in the late afternoon or evening, OTOH, would keep me from falling asleep.
My digestion just isn't quite the same after my gallbladder came out and coffee is enough of an irritant to trigger stomach issues. Lately I've cut back to a cup in the morning maybe every 2 or 3 days. Looks like I can handle that.
Always good to test things out to see how what works best for you. Everybody's different and our bodies also evolve as we age.
Hope you enjoy your extra sleep. 
