1 and 3 are the same, as your membership miles will be resent in any event.
Another way would be campaigns to incite you to fly, such as get 2x membership miles for BD operated flights over a certain period, as they have done recently.

Yet another way is a one-time buy-up for cash, like they do for BD *S, which has the advantage of putting cash in BD's coffers when revenues from flying are falling.