runninaway is quite right about the economics. Unless you are going to redeem miles on international travel in biz or first, and can do MRs which net miles at exceptionally low cpm, it probably is a losing economic proposition. Now if you fly a particular airline a lot already and want to achieve status on that airline; or, if you are within striking distance of a big award, e.g., a transpac in biz or first, and want to MR to get the additional miles needed; or, there are other special circumstances, that may be different. But do the numbers first to see if it would be worth it at say 3.0 cpEQM, which is a very "economical" MR, and one you won't find so easily.