When my wife and I generally play with her family, we may only get about 1-2 turns spending time with aircraft or taking advantage of our new found level 4 techs and modern wonders.
Once we played with 5 additional level 1 starting techs, and requiring three level 4 techs to win a space victory.
It seemed to work pretty well, with the same four victories within reach. Has anyone tried anything like this?