I sent out my save the dates 16 months ago, and our wedding invitations in January. Tomorrow is our RSVP deadline. As of this morning, I still had 181 out of 270 guests who had not RSVP'd.
I enlisted my mom and bridesmaids, and have gotten it down to 118 guests who haven't RSVP'd yet, but honestly - it is not that hard to do. I don't understand people not RSVPing, or even just telling me and I'll RSVP for them!
I'm also surprised by how many 'no's' we're getting - everywhere said to expect 10-15% - I am sitting closer to 33%! A lot of people have work interference - but in my mind, it they had wanted to come, with 16 months notice, they could have booked it off.