Just this year? If so, I'd say move closer to work!
Since I know this has taken you several years, congrats. I rode ~3,500 miles this year commuting, but don't keep track enough to know the totals for the last 6 years that I've been riding.
My goal, which I've reached the last 2 years is to put more commuting miles on my bike than my car. My job requires I be mobile some days, so I can't ride everyday, but 4/5 ain't bad.