The exact same hardware sitting in the same exact spot would get through 250 generations in 3 days.. and then the next set of 250 generations would take 5-7 days.
So it's not useful for testing out the speed of a machine.
It'll satiate your curiousity about how many generations have been produced since the last time you looked at the machine.
If you want a repeatable benchmark - take a look at the benchmark thread, and run the DF benchmark and try and figure out what the numbers mean.. *grin*