I commuted 18 miles one way on a Trek XO1 cyclocross bike.
When I couldn't because of client meetings, weather, I would park 1/2 way and ride.
I had access to a shower, and the bike stayed under a nice porch.
I eventually got a Trek 520 with fenders, racks, panniers, etc.
18 miles is totally doable. I had some good hills... including 2 miles out of the valley to get to my house.