Your Blue membership will not expire unless you decide to leave the scheme.
Gold membership is valid for 12 months and will continue at that level if you earn 15,000 points within 12 months.
Platinum membership is valid for 12 months and will continue at that level if you earn 30,000 points within 12 months.
Gold members who do not earn this number of points will automatically be downgraded to Blue membership.
Platinum members who do not earn this number of points will automatically be downgraded to Gold or Blue membership, dependent on the number of points earned.