My friend was given a delta e-voucher US$250 (Redeem at Delta.com. Elgible on Delta/Delta Shuttle/Delta Connection, Air France, KLM and Delta designated codeshare flights). expiration is about 6 month from now. What I am suprised is that the voucher can be used as a mileage certificate of 25,000 miles while mailing to delta, what is the best use normally for this type of voucher?