This is how you can keep a cold indefinitely :

• Take medicine
• Go to sleep
• Wake up feeling just a little bit better
• Conclude that you are totally healed and go do stuff (work, shop, or in my case, wander about in the cold with your camera).
• Repeat.

Yesterday I woke up thinking ‘I’m going to break the cycle. I’m going to stay in and kick this cold’. But then I saw the result of the ice storm and I couldn’t keep myself in. I went out again at night to get the blue hour/streetlight effect. I got sick again… but it was totally worth  it ;)