Answer:
When you need me, you must find me. When you find me, you no longer need me. What am I?
What gets bigger the more you take away?
I am a rock group with four members. All dead one was assassinated.
I am a seed with three letters in my name. Take away the last two and I still sound the same.
People need me yet they give me away every day.
Keep doing me to avoid lens dryness