I've figured out by play-testing a test map that future techs give 1 point each. With my current HoF Chieftain game (playing as France), I've figured out that even with 38 future techs, I still will only have about 5 points end-game score due to future tech, out of about 7,075 total. My advice: Once you get Genetics, and if you still have Civ's around you want to take out, Robotics and/or Synthetic Fibers as well, set your science slider low and increase happiness and/or tax revenue. If you wish to build the spaceship, of course get all of the techs which have parts before setting the slider lower. Going for future techs is a complete waste of time.