Hardly ever. There was an offer last year for 13 months at the price of a regular 12-month pass. Great for people who could actually use that 13th month. Meaningless to those who didn't because the price remained the same as a 12-month AP.
As far as offers for getting a discount on the price of an AP, the answer for the general public would be NO. FL residents and DVC members get a discount with proof of residency/ownership. You can purchase a regular MYW ticket at a discount from one of the online sellers and then use it to upgrade to an AP at guest services. Then use Disney GCs that you obtained at a discount to pay the difference.