A 100 % bonus on purchased miles is no good if the cost of awards doubles before you get to use them. (travelcodex.com)
Previous sales have offered higher bonuses, and at one time the base cost for purchased miles was lower. (travelcodex.com)
Often when purchasing miles during a promotion period, you don't get the best promotional bonus rate unless you purchase a significant amount of miles from the top tier of the promotion. (uponarriving.com)