If you want a few longbows earlier you can use an emissary to bribe those Welsh rebels and make them your own. That's the only way to have longbows before 1205. As mentioned, many other units also have time requirements (either times they can only be built after or only before). Another important one is halberds/swiss halbs/billmen and the entire Janissary line, both of which are only available after high.

Ajax