1.7 cpm is about as good a deal as American sells miles for. However unless you have a very specific redemption in mind and you come out significantly money ahead vs paying for the fare (which will also earn redeemable and elite qualifying miles, both you are giving up by buying miles), this doesn’t seem like a great time to buy speculative miles just to sit around for “some day”. Cash fares are low and who knows when truly aspirational redemptions will be accessible again.

If you have a specific redemption in mind, like two round trip business class tickets to Asia for next fall, let’s just say, it is simply a matter of how far ahead you will end up vs paying the fare, and if the savings is worth giving up the earnings of a paid fare.