the miles directly earned doing the mileage run are, for me, just a positiv side-effect.

the so-called 'mileageruns' will put me a status level higher (example UA 1K with NorthAmerican- and sytemwide upgrade vouchers, etc.) - but also the (mileage-run) trip should, in itself, add some fun for me (a meeting with people I otherwise would miss, visit a new place, revisit an old one) - and during the trip (if not sleeping) I will read a book I otherwise could/would probably never finish.