I have burned miles in the Marketplace before and need to again. At one point in the not too distant past, I had nearly 5 M miles in my SM account. Between flying a ton, elite bonuses, hotel bonuses, AmEx spend and miles, Sky Miles dining, etc. combined with lack of time to travel personally, they add up extremely fast. DL also has some cool 'once in a lifetime' experiences for auction on occasion, I've never done one of these but the OP may enjoy it!