recently purchased 30000 MQMs on UA for 3100
have to feed two high level FF accounts now - UA1k and DL diamond.
it took some of the stress off and gave me additional regional UGs now.
it's a shame that they are charging you almost twice what I spent and no rollover. :-(
if you ever need miles before the end of the year, just book a mileage ticket (assuming you are at the premium level where you can cancel without penalty), click add miles and choose the MQM mileage purchase upgrade. (three times the mileage being flown.)
then cancel the ticket. the mileage purchase remains.
Note that the price, for whatever reason) is different for different tickets, even though you are purchasing the same mileage.
watch UA, though. they require that a certain percentage of MQMs earned are flown.