I would say do the 2,500 mile trip to play it safe - using google flights, you can probably find a trip of that distance for not much more than a 1,000 mile trip. If you had IRROPs and you got the bonus because an agent rebooked you in F or full fare Y, it will stick. Otherwise, this is the type that might get reversed if they audit your account and you don't want to be sitting there saying, gee I wish I flew the extra 1500 miles for an extra $50. I think there was a thread a while back regarding account audits and DL does do them from time to time.