It really does help knowing this far in advance so you can buy everything you need per person, know what you budget will be and plan accordingly. I am very happy I did it this way. I am also getting some maybes for the AHR in July which is totally understandable and there is one week left till the deadline on the rsvp card and I am still missing just under 2/3rds of the replies so even if they come in late it won't be a big deal. At least the people have been told and have an option of a guaranteed rate with only a 200$ deposit. Big hug back at ya!
Glad to hear I'm not the only one who was a wee bit demanding! We also sent out our invites in July (1st week) and gave our guests until September 1 to RSVP for our April 7, 2011 wedding. Similar to you, we did not want the added costs of sending 2 invites and had a group reservation booked that was only guaranteed until September. I definitely agree that people either know or they don't, if they are going to be able to go or not. This has really helped us with planning and although we do still have a few "maybes" (which we are ok with), it helps give us a pretty good number of what to expect in Jamaica.