You've pointed out the big problem that I wasn't addressing...mail order!

On the retail level, we have done many nationwide and state plans (probably 25 states) There are exceptions to the rule, but they are usually a surprise and I certainly wouldn't estimate it as a significant portion of nationwide or state plans that don't follow the 80% rule. The biggest of the national pharmacy benefits managers (Caremark, MerckMedco, ExpressScripts) follow the 80% rule at retail pharmacies. However, as you've accurately pointed out, mail order has its own set of rules. They do not seem to follow the 80% rule. A 3 month supply seems to be able to be filled only a few days early. This is IMHO dangerous to the patient because of the chance of missed doses.

I can't tell you how many times seniors come to me for a two week supply because his/her mail-order outfit dropped the ball. They'll lose prescriptions and just claim that the patient never mailed it.

It's sad that many insurance plans force the patient to go mail order. If you are unlucky enough to be forced into that, it will probably make more sense to get a separate prescription and (if the insurance refuses to fill it) pay full price. Of course, look for deals at Costco, Sam's and other outlets. BTW, you don't have to be a member of Sam's or Costco to fill a prescription there. Many don't know that.