DBDC has many relationships with many alliances, many of which have significant upper tiers. The alliances best in a position to destroy DBDC are also unlikely to do so because of these connections. However they all have something in common: most view DBDC as a partner of necessity to keep their upper tiers safe so they can focus on other threats and keep aid flowing. However, they all share a common interest, being significant upper tier forces, in preventing DBDC from becoming too much to manage. More importantly, DBDC needs to raid in the upper tier to survive but most of the nations in their range are in alliances with whom they share a connection or are in neutral alliances and are too strong to attack. Eventually they will be forced to attack those nations in the non-neutral alliances with whom they have a relationship of one kind or another, and those alliances may feel they share a common interest in destroying this threat.
Even if they don't, DBDC has to raid to survive and thrive but also has to keep connections with those that most pose a threat to them. This is a very tenuous situation as is a string under tension, one prick of a pin and it will snap. DBDC could avoid this by gradually reducing the number of those connections keeping just enough others on their side to avoid destruction while neutralizing the threat posed by those they drop. However, a sudden blow against too many of them will likely prove disastrous. This is an incredibly fine balancing act, one unlikely to be executed successfully. The fact is that too many things can go wrong, and when so many things can go wrong, something probably will go wrong. Given this, I find it likely that DBDC will not survive for as long as many think. But there is a caveat to this prediction: if DBDC changes their game such that it no longer needs to raid to keep thriving, none of the other problems will exist in a state of tension and the alliance's situation will stabilize.
Let me close by stating that this is just my view of the current situation, and is not intended to represent the views of my alliance or anyone else. More importantly, I'm not necessarily hoping any of this will come to pass (though it'd probably be fun if it did because, well, war ), but looking at things it seems likely that it will.