One thing that I would take into consideration is if you have any family or friends out of state that could necessitate potential last minute travel in the future. For example - if you have elderly parents out of state, chances are you may one day need to get there quickly and as you know, last minute fares can be pretty high - even the emergency fares. But - with the miles, the most you would ever have to pay is the last minute redemption fee (at Delta $75.00.) Just a thought to consider.