One (minor) catch on SWA. If you change your booking and you have extra money leftover (the new price is cheaper) then you get a credit that has to be used within 1 year. And not just SPENT within one year. You have to have a flight that occurs less than one year from the PURCHASE DATE of the original ticket.
However, barring that caveat, yeah there's no change fees. My personal take, if I see a price that's good on a date I MIGHT want to travel, I book it. If I need to change to a different date and the price is higher, I'm good.
SP