I have a college domain and it was earning good revenue from parking for the past three months. It used to earn anywhere between $0.5 – $2.5 per click. For the past few days, each click is earning $0.01. Thats a huge difference. Its right now earning next to nothing. The point i am trying to make is some niches perform only at some season. The best way to reduce the risk is to have a diversified portfolio. Spread your portfolio is the key.