The term you were looking for is "extrapolation" and it's still incorrect. I am a big fan of health insurance. The costs of keeping enough liquidity to be prepared for the worst cases covered by health insurance is higher than paying health insurance. The required liquidity for the latter is much lower, because there is enough inflow of money every month.

My point is, if you have multi-GH/s power you can afford solo mining with its better average returns without too much risk of never finding anything. If you have less hashing power, the return of pooled mining is too wimpy to be worth the hassle (if you aren't a kid) and possibly risk of investment (even tighter increases of difficulty or price drops). Mining solo is fun on the other hand. You either write it off after a while (0.5 BTC/day wouldn't have changed much) or you jump in circles over $750 in you wallet after waking up.