Very early miscarriage how soon is too soon

We recently miscarried in about our 5-6th week. We previously had an ultrasound (vaginal) seen the sac, was rescheduled for 2 weeks. Unfortunately miscarried naturally 6 day's later. Seemed as a normal period with a few small clots. I've heard Dr's want you to wait for 2 cycles, (miscarriage is that of a cycle) so they can be more accurate on your pregnancy data. What do you think? How soon is too soon.