This would be a good study, because after thinking about it, I could see why they might consider adding that factor into an algorithm. Sites come and go, but ones that stay around longer may seem more relevant. As everyone said above, older sites naturally have more backlinks. One would need to compare a slew of older sites with new ones, and the first set would need the same number of backlinks as their counterparts for a fair study.

On the other hand, I know googlebot comes around more often to sites that update more frequently, even adding newer pages. So even if the theory is true, the old timer needs to still have a pulse.