Most of my typical games are at parties I host for the purpose. Usually Battalion v Battalion, 500 points per player, 3 players per side, so 1500.
The best Batt v Batt game I played was 40 units v 40 units, 1500 pts, 8th Lyran Regulars vs. Mercs, Civil War Era with Battlefield Intelligence, Buildings, most of the optional special abilities, SCAs,Force Building/Formations and pilots with purchased SPA's.
Me vs another experienced player. Took 4 hours. Great time.
Upcoming, a friend and I are doing a slice of the Battle of Geneva from Liberation of Terra II, 99th Amaris Dragoons vs. 27th Royal CAAN Marine Regiment.
1500 points for the Dragoons (me) vs 1875 for the CAAN (him). Me defending in a "hold them off" scenario at La Jonction where the Rhône and Arve Rivers meet. Dawn battle in the fog as the SLDF probes the Dragoon lines trying to find a place to force a crossing and the SAS slide in to lock down some "asset management weapons" I'm guarding.
44 units each side, but he's heavier. Mix of vehicles, infantry, Mechs, and LAMs on each side. Tons of optional rules. I expect it to go 6-8 hours the first time, but since we're practicing for showing it off at a con, I think we can get the time down to five.
Will be fun playing with all the crazy stuff....LAMs, Kangas, a company of Ignis tanks, SAS in Nighthawks coming in via Cyrano Furies, and....The 'Mech...The Myth...Rifleman III, with a Buster LoaderMech humping ammo for him.
I'll let you know how it runs.
EDIT: I always run on at least a 4x6 foot table, if not bigger.