You will get this achievement during the Career main storyline and it cannot be missed.
After winning a Career Championship you have to select another contract. You need to either choose to renew your contract with the team you were with, or pick a contract with another team from the same class and then win the Career Championship again
You can get this achievement in less than one and a half hours using this solution. When the season starts skip all non-championship races, practices and qualifying. Before starting Round 1 Race 1 change the Session Length to 1%, and if you want to make it easier you can dial the opponent skill down to Beginner. This means you can win each race in 5 minutes or less. When Round 1 Race 2 starts, pause and select Retire To Pit Box
then Skip To End Of Session
. If you want to be really cheap, you can take out the driver who is in second place in the championship before you retire. Keep winning Race 1 and if you are 26 points ahead you can skip Race 2 until you reach the end of the season.
However I recommend you do this after winning a Tier 1 or Tier 2 Championship, and that renew your contract with the same team.
• LMP1 World Championship (Tier 1)
• Formula A World Championship (Tier 2)
• LMP2 World Championship (Tier 2)
• World Endurance Championship (Tier 2) very time consuming, so I would avoid it
That way after winning the same Career Championship two years consecutively for the same team you will also get:
Win the Championship again for the same team two more years in a row and you will complete one of the Historic Goals, and get:
The best time to go for this achievement is right after completing another Historic Goal:
That way you will only have to win the same Championship 3 more times.