There's also a tweak I would make to eliminate a (very small) chance of failure if the file is put out there literally at the last second. Change

...

If Now() >= NewDT Then

Dts.TaskResult = ScriptResults.Failure

Else

Dts.TaskResult = ScriptResults.Success

End If

...

to

...

If System.IO.File.Exists(Dts.Variables("FlatFileConnection").Value.ToString) Then

Dts.TaskResult = ScriptResults.Success

Else

Dts.TaskResult = ScriptResults.Failure

End If

...

This way, the success is dependant on the real thing you want to check (i.e, the existence of the file). Otherwise, if the file arrives at the last second or some other performance issue causes the task to run slowly, you may get a failure even with the file out there.