Hopefully quick question- I need to go on two very short 3-day TATL round trips (EWR-LHR/LHR-EWR) one in March and one in May. Trying to price such a short TATL turn-around results in the expected extortionate fares (like $3k in economy extortionate) that the airlines like to charge desperate business travelers.

But is there anything practical or in the United T&Cs that would stop me from instead booking a very long EWR-LHR/LHR-EWR trip and another very long LHR-EWR/EWR-LHR trip nestled inside it? Thereby saving about $2500 per trip. Am I missing something obvious?