I also had many years where I flew sporadically and took whatever airline was convenient. I started with the FF programs early, though, accumulating miles because "you never know". (That was back when it took a long time for them to expire, if at all.) It paid off when I was able to take my 12-year old son to a conference in Bermuda with me on FF miles. So, even infrequent fliers can reap the occasional reward.