I had a 20mi rt commute on a SS which I did 4 days a week. I would hop light rail most days. When I did not, my RT commute was 62 miles.

Things I learned:
- I hate to ride with stuff, I am a roadie at heart. So it required that I drive to work twice a month to "stock" my office with enought clothes and clean towels to get me through the month without carring a backpack.
- 60 miles in the rain was not that fun after about 15 miles into the trip. Even with full fenders and good rain gear, my shoes were soaked at mile 15 and by mile 20-25 I was pretty soggy myself.
- Nice days make for a great way to unwind, and I found that my commute took me about 30 min longer than had I driven. Not bad.
- That kind of distnace means you need to consider a good light setup. Depending on your average speed and your work start/stop times, you will likely be riding in pitch black for part of your commute. Factor in at least $125 for a decent F&R light. (I ran a Dinotte 400L, Magicshine 900, and 4 PB Superflashes.... and I still want more light)

You can do it, it just takes more work, and a good plan for a decent lunch since you will need the energy to get home.