I'm not sure what IAS is,but for the individualized tests like WISC and SB(Stanford-Binet), it's going to depend on the tester and the kid. Some kids need more than one session as they could be fatigued or distracted or bored at some point. I've seen a lot of people mention the WISC running across 2 sessions. For some reason school psych used 5 sessions to do SB with my DS, which seemed excessive.