The DEP is only run seasonally. It goes "dark" (doesn't run) after Labor Day. It will then come back for a brief period (about 2 weeks) surrounding the holiday peak season. It then goes dark again until Spring Break peak season where it will run nightly for the 2 weeks surrounding Easter. After that it runs on weekends only until Summer peak hits in mid-June when it will start running nightly again.
So, if you are planning a trip this fall, you won't be seeing it.