IDIQs and duration of option year policy

I have read the FAR, DFAR and AAFARs Parts, Subparts on IDIQs and Options, Options on schedule contracts and non-schedule contracts. My question: Is there a specific policy that is current that speaks to the requirement to use the base and 4 options years instead of the 5-year order period for task/delivery orders?

Please advise and I greatly appreciate any advice and/or direction quick. I, of course, am trying to find specific policy language in the FARs that speaks to which way...is the policy now; is it 1 plus 4 option years or is it still the 5 year timeperiod?

Thanks