I just let my 3 months expire and then asked the chat CSR if there were any offers available on my account. He checked, and offered me 3 months of Starz & Platinum HD (again).
I still have Starz free so I'm going to wait 'till it expires to try again. Plus I hear DISH is offering a year of free Starz so I might just wait for that whenever it kicks in.
I just noticed that my 3 months expired, went in the online chat, had to play CSR roulette (once) and asked about the free HD Plat. for 3 months, and success !
I just got Starz and HD platinum free for 3 months too. It's my first time. I already had paperless billing and autopay, but I just went on chat and nicely asked for it and got it in minutes.