IMO, there is no substitute for having a stash of miles equal to the minimum cost of a ticket you would purchase. For example, my wife goes to Europe every summer. Even if I was going mostly for cash back, I would still make sure I always had 60,000 miles (on some airline) available. Even though availability can be awful sometimes, you just never know when you will get lucky and find a ticket that's a real bargain with miles. Of course, having points that convert to miles is just as good.