This document outlines the timeframes Kyle mentioned for acute and chronic unilateral vestibular hypofunction (3-5x/day for 12-20 minutes), although the strength of the evidence for these general recommendations is weak.
On page 38 of the PDF, you can see the evidence updates for acute/subacute and chronic unilateral vestibular hypofunction. One individual study used a duration of 1.5 minutes for VORx1 viewing. Another study used a shorter episode of PT but increased frequency of VORx1 exercises (10x/day). I didn’t see clear guidelines regarding the rate of head turns in this document.
Basically, there is strong evidence to support VORx1 viewing for vestibular hypofunction and there is a trade-off for rate of head turns and duration. Like Kyle mentioned, long duration VORx1 viewing isn’t necessarily functional. I always consider functional complaints and assessments as I progress/modify my VORx1 recommendations (i.e., what are the patient’s scores on other objective measures, how is their reported balance during home/occupational/leisure activities, etc.).