Since all of our air travel has to be booked through a corporate TA, the use of airmiles is not possible. The only restriction we have, is that we are forbidden to book a certain airline for the expressed reason of gaining miles/status on that particular carrier. We are always to book the lowest option (or within $75 of it).
Since most of our trips are booked 7 or less days in advance, it would be pretty hard to use miles anyway (especially on CO where most of mine currently are) since availability is pretty poor at that point.