This achievement really requires 8 people who are interested in earning it to meet up online, set up a 5 minute season, and hope that no one is disconnected during it.
No one plays this legit online, so unless you schedule it, you may never earn it.
Elem3ntal80 adds: "I managed to set this up with 7 others...for us, a second on the game clock really took about 3-4 real time seconds, so the game might actually take 15-20 min to complete."
However when I had scheduled this achievement, it only took the game clock, leading me to think it's buggy for some.