i've done this in the past.. I used IAD-IAH-LAX and back.. I bought a discount fare requiring a Sat night stay well (2 months) in advance.. the duration was for two weeks...

About a month prior to taking the trip, I saw a CO fare sale LAX-IAD for some dirt cheap amount. Since I wanted to rack up some EQM's and go home as well.. I booked it for a Friday departure/Sunday return.

CO never said a word..

I felt that since I bought these tickets a month apart, I was not cirucumventing any rules b/c of the timing of the purchase. My arguement (whether its true or a lie would be the same) would be something came up.. I had to go back.. you happen to have a fare sale.. and I bought it.. my arguement would have also been I would have bought a ticket at ANY price (for the middle weekend trip) due to circumstances unknown at the time.. I am not a lawyer but I'd like to think that this would hold up in court as not circumventing the rules.