I recently started a game as Teutonic Order in 1444, joined the Holy Roman Empire and allied to Austria. As usual in the first 5 years Poland declared war on me and with the help of Austria and Hungary I defeated them and took 2-3 Polish provinces in the peace deal. I made sure to fabricate claims on the provinces I took before the war. Soon after that a coalition involving Sweden, Bohemia and a few minor countries attacked me, and again after winning I took a couple of provinces that I had a claim on. And again a new coalition formed against me, so it seems like an endless cycle. I took land I had a claim on in defensive wars, and I could have taken a lot more if I wanted to but I did not to avoid acquiring aggressive expansion and save administrative points I would have to spend on coring.