Hard Drive lifespan

Nope.

vidgpersonrsw wrote:
What is the average lifespan of the default hard drive that comes with the Alum. Macbook? Is there anyway to estimate this?

The manufacturer likely has a "mean time before failure". Most publish a "useful life" around 5 years but the MTBF will be in the hundreds of thousands of hours. That frankly won't tell you that much. There's a huge distribution of hard drive failure times. Some failures are purely random or a result of accident, while others are from mechanical parts wear. I've seen hard drives that showed signs of failure but could be coaxed into sort of working condition. I've seen other drives that failed unexpectedly.

Your best bet is to perform regular backups, because it's not a matter of if your drive will fail, but when.

The five year life is used by the US government for depreciating personal computers and associated equipment. The "five year life" does not refer to the wearout of computer equipment, rather it's an "economic life" - a period at which it is cheaper to replace than repair. If you assume 2500 power-on-hours/year (10hrs/day, 5 days/wk, 50 wks/year - and an HDA MTBF of 250,000 POH, 1.0% of the HDAs will fail every year. If you assume that the computer is on all day/every day, 3.6% of the HDAs will fail every year.