This is what the website says:
After 10 consecutive years at Platinum level, you are entitled to a lifetime Platinum Card.
In that case, whatever your mileage accrual and the number of flights you complete each year, you stay a Flying Blue Platinum Member!
I am not sure how to interpret this....is it 10 consecutive
calendar years at Platinum Level or 10 consecutive years Platinum level from the date of achieving Platinum? That's the difference between year of achieving plat for the first time + 9 , or year of achieving plat for the first time + 10.