Originally Posted by
Eszpresszo
.... So, I am curious if there are specific scenarios where you benefit from this more than others. ...
General recommendation is don't buy miles (even if on sale) unless you have an immediate use.
Make sure you are getting more value than the costs. Lots of awards are 1 to 1.5 cpm while buying miles > 2cpm, bad deal.
Buying a few expensive miles might make sense if you are topping off your account (short just a few miles) to make an immediate purchase.