I have a feeless Delta Amex card, and have resisted continuous blandishments to upgrade it to something that carries a fee. I use it exclusively for double miles purchases (the specified categories and then the occasional double-miles-for-everything promotion). I think it's worth keeping for those, but not if I had to pay for it. I think it would be quite some time, if ever, before my accumulated miles became worthless, and I'd hope to use them well before then (hopefully on a foreign partner, as I really dislike Delta).