The two DM choices must be taken together. They can be taken until the Medallion year ends (Jan 31, 2016 for next year). Only one can be RUC or GUC, the other must be something else. They expire 12 months after they are chosen, so waiting is good.

Your friend won't get one for this year and one for next year, that loophole ended a couple of years ago. Just one for the first year you make it, even if you get more than 12 months of status.