The routing subtests help, but don't eliminate this, especially if an examinee performs quite differently on different subtests. Strictly speaking, he probably did not get through four or five subtests, but may have completed four or five testlets. There are multiple levels of each subtest, and a verbal and nonverbal version of each index (so 10 subtests altogether, with five levels of the eight that are not routing subtests).
He probably is taking a long time because of a combination of factors, including being conscientious, and doing well.
BTW, there are extended norms for the SBV, which you should ask about, if his IQ ends up being upwards of 145 or so, or if he maxes out a couple of subtests.
