Go into a planet
Make sure no priorities are set(social, military, research)
Build a buidling.

Now it might say that it will take 60 turns to build this building.
Set priority to social. (might say 7 turns now)
turn off priority again (instead of going back to 60, it will go to like 8)

So now everytime I build something, If I don't switch priority on and off I will have a ridiculously long build time.

This could be old news, I don't keep up on the forums.