I don't have a definitive answer to your question but I think it's a few months beforehand. DH and I are headed to Hilton Head in November and I was able to book a member discounted 5 night stay just last week so that's about 2+ months out. I'm happy we were able to get the discount but something a bit odd happened. I called to inquiry about 1 bedroom villas but I didn't want to book anything right then and the MS agent told me she could pull up 5 in her computer with the discount. I firmed up the plans with hubby that night and called first thing the next morning and was told that all the one bedrooms were sold out period. Not even at full price could I have one.
Fortunately the price difference is only $10 per night so we're in a 2 bedroom but it seems like a waste for 2 people to be in a villa that sleeps 8. Oh well, we'll enjoy spreading out!
Anyway, I hope you get your discount - if they say it's available when you call, grab it - it could disappear if you wait and call back later!
