NickB

It used to be the case that the only way to extend miles was through an activity that generated what as then known as 'status' miles (now XPs), i.e. essentially flying on a revenue ticket (or spending on some affiliated credit cards).

That system is still in force for miles acquired through flying or miles acquired by any means if there has since been some miles-earning flight activity. Most people here are AF/KL frequent flyers and therefore their experience will match that situation. I suspect that is why they only consider revenue flying or affiliated credit cards spending (or XP crediting) as valid moves to stop expiration.

What has changed in the last few years (can't quite remember when the rules changed) is that, for miles credited to the account exclusively through non-flight activity and where there has not been any flight earning activity since the miles were earned, the miles can be extended through non-earning activity. So, for a minority of FB members who do not earn any miles from flying, there are indeed alternative avenues to stop expiration. Clearly, FB miles earned through hotel or car rental partnerships, FB shopping portal, etc... would clearly qualify. I do not personally know whether credit card transfers themselves do qualify for that purpose too but the threads I referenced above suggest that such transfers do indeed qualify. As I do not have any direct experience myself, I would not want to take a position on this, hence my suggestion to peruse existing threads on the topic.