i just had the same case of may 30th and the system downgraded me instantly at midnight Hong Kong Time on June 1st to Gold. then i had to fly and wait for my trip to be credited to call them back and get the upgrade back to DM. Once they verify it on the phone, the upgrade to DM is done on that day itself within a few hours....

I beleive there is no grace or exceptional allowance on renewal anytmore as i was only 3000 miles short of DM and they didnt automatically renew...but if someone has any different experience....please do share.....