Following establishment of this initial mail classification schedule, a 3623(b) provides that the Postal Service may from time to time request that the Commission submit, or the Commission may submit to the Governors on its own initiative, a recommended decision on changes in the mail classification schedule.
The mail classification schedule is changed very frequently. 
mnli hypothesis: The mail classification schedule is changed very frequently.  premise: Following establishment of this initial mail classification schedule, a 3623(b) provides that the Postal Service may from time to time request that the Commission submit, or the Commission may submit to the Governors on its own initiative, a recommended decision on changes in the mail classification schedule.