You don't say where you live, but presumably it is LAX (perhaps time to update your profile if you are going to be asking questions like this). If all your NA flights are just for MR and you don't care where you go, then you are wasting about 50% of the possible mileage. Lots of past discussion of the high-mileage routes available (ironically many of them are through LAX). Also you can open-jaw, so you don't have to continue from SFO. You could fly sfo/lax-jfk-sju-lax-dfw-anc-lax for 15K miles, for example. Lots of other alternatives, depending on taste and season (e.g. SJO, AUA, SXM) which would yield 15K mile range.