I support birth-month biennial renewal.  Licensees renew every two years by the end of their birth month.  Individuals born in even numbered years, renew no later than the end of their birth month in even numbered years.  Individuals born in odd-numbered years, renew by the end of their birth month in odd-numbered years.  This spreads out the workload of renewals across a longer time-frame, as well as makes it easier for licensees to remember when to renew.