I have found that early/premature abstraction generally has the opposite of the intended effect. Rather than making the system open to extension and flexible, it pours code concrete around the concrete classes and the interfaces. Invariably, the interface ends up with every public method of the only implementing class. And methods taking "SuperInterface" which only use a subinterface of that interface can't be untangled without a ton of effort.

Meanwhile, if you can figure out small reasonable interfaces with potentially multiple implementers, then all the sudden things get a lot easier to deal with.