I look at the times of each event, the proximity and any overlap or gap. I try to eat heaviest (if there's food) at the first gathering and the next to last gathering (sometimes it's the last). I don't stay longer than 2-3 hours at any place to allow for travel and debriefing. My plan works best of all of the events are in the same city or neighboring cities. If I want to attend something further away, I adjust the time at the previous event and sometimes eat and drink more.
I have been doing this for over 20 years. For events (including holidays), my personal best is 6 houses(places) per day. It makes for a long day but well worth it when I want to see and be around certain folks.