You can do "pseudo" back to backs and it is very difficult or impossible to track. For instance, on ridiculously expensive routes, you can book on 2 different airlines (try to use ones that have different reservations systems, UA-Apollo, AA-Sabre). Throw away the return part of the ticket and in many cases you can fly two or three people for the price of a single flight during midweek.

Be careful though if you travel on business and change plans often. The tickets may have more restrictions but usually with paying the change penalty you still save $$$.