It has long bugged me that the eras feel as if they are 'flying by'. A few turns I'm in ancient times, then already classical era starts. If you're beelining, tree techs later you are already in medieval times. It feels weird. Somehow I feel I should stay longer in ancient times, with brutal warriors, pyramids & primitive pantheons - literally for "thousands" of years. And then, classical era with hoplites & legions should also take their time. I think I have finally identified the reasons I feel this way: (1) the ability to beeline strongly - which allows you to rush ahead 1-2 eras (2) the splitting between the tech & culture tree. Because of that, every era only has ~8-10 techs (in the science tree). Of course, if you combine both trees you get 15 techs, which is more appropriate. But since they are not interdependent, the eras feel less fleshed out. The few techs per era also make beelining easier, which adds to the feeling that eras are 'rushing by'.