My wife and I spent about $4,000 on miles in August when UA was doing a 75% promo. With the (somewhat minimal) miles that we had, that gave us enough miles for two C awards to Southern Africa. I wanted to fly into WDH and out of either LVI or VFA. Economy class tickets were all somewhere around $1,800. Instead, for $200 more per person, we're flying in C the whole way and we got to take advantage of the Excursionist Perk to take a side trip for a couple days in the Seychelles. Well worth spending the money on the miles, but I did book the award one day after buying the miles. With the rampant devaluation, it certainly doesn't make sense to buy miles speculatively.

Chris