Oh, sure. You can refare as many times as you like.

Whatever fare rules you're under will apply each time you do it, of course. On a $590 ticket with a $150 change fee, it's probably only happening one time. In this case, OP gains the benefit of a small net gain (assuming he will use the residual credit) as well as changing his dates. But from his $391 ticket, it's unlikely to happen again...unless someone drops a $99-each-way fare sale on SFO-MCO. Even then, you'd have to ask whether $150 in right-now cash is worth more than a slightly greater amount in credit that must be consumed by a fixed date.

I've refared the same Southwest ticket twice on a couple different occasions.

A question, because I don't know: what major airlines give their top-tier elites free refares on nonrefundable tickets that would cost the rest of us $150 to change? And are there any airlines that have some sort of lesser or no refare fee for non-elites? (e.g., Entire itin remains identical...purely a refare.)

Long ago, I remember visiting an AA CTO as a mere Platinum and refaring tickets, generating small vouchers to use later. No fees. I'm pretty sure Golds/Plats don't have this benefit anymore. Do EXP's?