BD requires a total of 57k to hit Gold. Status is then valid for a year.

Then once you have achieved 55k status miles as a Gold, any status miles over this are converted to destination miles. BD also give a 25% base mileage bonus on destination miles on all *A flights.

The only concern is that within the next few years, BD diamond club may be converted to Miles & More, as Lufthansa is now the primary share holder.