Diamond Club Terms & Conditions
(termination)
11.3
Members who have not recorded any activity with bmi, its diamond club partners, or made a redemption with the same parties and other promotional third parties, for a 12 month period, from the date of their last recorded activity on the diamond club database, shall be deemed dormant. If no claim is made on any residual Destinations Miles on that member’s account, membership may be terminated after a further 12 months and all remaining miles forfeited. When your membership is inactive you will not receive statements nor other diamond club mailings.
http://www.flybmi.com/bmi/src/aspx/p...sandconditions
I hope that helps.