title: How to delay items, but only once in the beginning?
body: <p>The <code>delay</code> operator delays all items by the specified amount of time. I would like to delay and buffer items only for the first N seconds. After N seconds there should be no delay. I need to do this in the following code.</p>
  
  <pre><code>private Emitter&lt;Work&gt; workEmitter;
  
  // In the constructor.
  Flowable.create(
          (FlowableOnSubscribe&lt;Work&gt;) emitter -&gt; workEmitter = emitter.serialize(),
          BackpressureStrategy.BUFFER)
      .observeOn(Schedulers.from(executor))
      .subscribe(work -&gt; process(work));
  
  // On another thread, as work comes in, ...
  workEmitter.onNext(t);
  </code></pre>
  
  <p>What I want to do is postpone processing of work during the first N seconds, but not after that. I tried delaySubscription, but it leaves <code>workEmitter</code> as <code>null</code> during the delayed period. The reason I want to do this is to make the CPUs available for other important work during the initial period.</p>