Stay in contact. I have one good client in all other aspects (pay level, pay timeliness, interesting work, etc.), but I have to bug the editor every couple of weeks or more to get assignments. I bugged him for six months before getting any work even though his constant lament was about writers missing deadlines — and I treat deadlines like the first commandment (Moses dropped the tablet with that one).

Have also found that such regular communication moves some prospects off the idea of “call back in a few weeks,” to “we don’t use freelancers” or “we rarely use freelancers,” and you can cut off contact (nicely) without losing the chance of work.