the simple answer is that your pre-taxes/fees spend on tickets needs to average 10 cents/EQM.

Silver = 25,000 miles and $2500 = $.10/EQM
Gold = 50,000 miles and $5000 = $.10/EQM
etc.

so, if you buy a 5 cent/EQM ticket for 5,000 miles, you need to offset that at some point in the year with a 15 cent/EQM ticket for the same or longer distance to stay "ahead of the curve". otherwise you'll end up flying more miles than necessary to get the status.

eg, if you want to earn 1K status and your spend in $/EQM = .05, you'd have to fly 200K to make the spending threshold.

the simpler answer is to do what i plan to do - stick a knife in UA's back, and twist.

MRs are now going to be the most useful for those who regularly book tickets (generally for business reasons presumably) at $.15+/EQM but don't make the mileage thresholds for a higher status tier.