We're sending out ours 9 months in advance since its a holiday weekend. Since yours isnt, I would say 6-8 month rule is fine, anytime once its 2011. Any earlier and people won't even have a calendar/schedule for the right year and your STD may likely be lost or forgotten.
I am doing exactly one year 1. all the guests are OOT 2. It's on a holiday weekend and 3. It's in Canada and you now need passports to cross the border so I think it's pretty important people have PLENTY of time to plan. But I agree w/ PP that anything more than a year is too soon.
Re: Save The Date Timelines
Dresses may be easier to take in than let out, but guest lists are not. -- kate51485
Christmas Countdown