Payment of benefits under the coverage enumerated in section 10-4-706 shall be made on a monthly basis. Benefits for any period are overdue if not paid within thirty days after insurer receives reasonable proof of the fact and amount of expenses incurred during that period; except that an insurer may accumulate claims for periods not exceeding one month, and benefits are not overdue if paid within fifteen days after the period of accumulation. If reasonable proof is not supplied as to the entire claim, the amount supported by reasonable proof is overdue if not paid within thirty days after such proof is received by the insurer. Any part or all of the remainder of the claim that is later supported by reasonable proof is overdue if not paid within thirty days after such proof is received by the insurer.