I always RSVP by the date. Normally with a card.
However recently I have received a couple of invites to events that are in 6-7 months.. Understandable if they were interstate but they are not.
I have no idea how I am going to be with a 2-3 month old baby or even how the rest of my pregnancy will go. My intention is to get grandma to be to baby sit and dp and i to go to the event, but as its our first child I have no idea how smoothly that will go lol.
I intend to get dp to talk to them about it as we are going to need some flexibility in the RSVP time.