We get married in May, and were planning to hold off until about March before sending out the evening invites.
We will be sending invites for roughly 120 people altogether (including people staying from daytime) and have arranged a buffet to cater for 80. I don't really need to know numbers, as our venue holds about 200, and I reckon a buffet for 80 would probably stretch to 120 - although we don't anticipate that absolutely everyone would be able to make it anyway.
Do you reckon it would be acceptable not to bother with RSVP. Or should we include RSVP details but just not bother to chase?