I don't have any desire to ride a century but have done my share of "metric centuries". My commute is roughly the same distance as yours. What I have found is hills and time in the saddle make a big difference in how comfortable I am on long rides.

I don't know where you live but in my area there are some pretty major hills and I can't ride 30 miles around here without a good bit of elevation gain. If I were you I would find out what the elevation gain of the century you're considering and get a feel for what it's like riding some of those hills. My commute is relatively flat and it would do nothing in preparing me for a 60+ mile ride with 3000 feet of elevation gain.