Join Date: Dec 2010
Location: northern Deep South
Bikes: Fuji Touring, Novara Randonee
Commuting is good because you ride almost every day. You might take a look at some of the century training plans to add some longer days, and try doing longer rides over the weekends. If you did 44 miles last weekend, try for 50 next weekend, then 55 and 60 the next couple weeks.
After you can ride 60 miles without problems, all you need to worry about is eating and drinking enough. I've pushing 10 years of centuries, and I think I've managed one in which I drank enough. (It helped that it was in February!)
Also try adding some variability to your commutes. Not necessarily the route, although you might add another 5-10 miles to the trip home, but intensity. Add a few intervals -- 30-60 seconds of riding as hard as you can -- to your commute 2-3 times a week. In between, catch your breath.
And don't worry about changing your bike or gear yet. If you need to change something, you'll have time to figure it out; maybe before your second century!