I commute 90 km and depending on conditions, it takes 3h30m on my best days (25km/h) and sometimes up to 4h30m (20km/h) when i haven't slept enough or there are strong headwinds. But i would say that i average 22~23km/h.
I wonder if i can get any faster, it's a lot of time on the saddle. Is 3h an achievable goal (30km/h) ?