I'm 30 years into an AS campaign and I actually found it really easy. The only factions to attack me were Parthia, Egypt and Saka, so I was able to concentrate my forces on two fronts. The only settlements I lost were Asaak and Antiocheia-Margiane briefly, as I focused my forces on the east in order to destroy Parthia in about four or five years, while also taking the Levant from the Ptolemies. After that it was basically just fortifying Alexandria-Eschate and Marakanda against Saka and destroying small factions at my leisure, as Pontos barely took Ankyra and just sat there all game while Hayasdan was busy with nomads. I destroyed Pontos in my conquest of Anatolia, drove Hayasdan onto the steppes, knocked Saka back to about 3 settlements in the north, and am about to take the Arabian peninsula. Definitely one of the easier EB campaigns I've played.