My typical route to work is 17 miles round-trip and takes me down a greenway and through neighborhoods to the office. I do have a couple of big hills I go over each way but, to tell you the truth, I don't mind the climb up the hills so I can experience the thrill of coming down the hills. I ride when it is hot (106 degrees) and cold (14 degrees with a strong headwind just last week). I ride to work in the daylight and normally ride home in the dark; I did invest about $300 in a headlight for the bike and have, in total, 4 very bright lights in order to stay safe on the roads.
Last August, I started tracking my mileage on a website called GasFreeCommute.com. Since that time, I have logged nearly 1600 miles. My blood pressure and cholesterol are great and I get a chance to think about how to make our software even better while pedaling. Today, I looked on the website and I am currently ranked 4th in miles this month among the nearly 1700 members. I think that is because it has been cold out but not too cold here in Alabama, especially for someone with as much Michigan blood as I have in me. Here is my souvenir snapshot of the website with my initials; I am sure my initials won't be there as springtime gears up and more people get to ride.
For those of you who can manage it, I highly recommend bicycle commuting even if you can do it only once a week or once a month. You will feel better for it and will help the environment just a little in the process.