I run a monthly 8 hour(ish) game. My last campaign was a megadungeon and for most of the campaign, the party had a stronghold they a day or two's journey (before they had magic travel) from the dungeon. Most sessions ended after the party accomplished something, or retreated, and end with them back at their stronghold. Occasionally, we'd end the session with them still in the dungeon, but it was very rare to end mid-encounter. I would rather end the session early and start the next session with the encounter than risk ending the session mid encounter.
My first campaign was home brew and each session was an adventure that could be completed within 6 or so hours.
The only other campaign I ran, and the only WotC one, was Curse of Strahd. That would often end on cliff hanger and often not in situation where a long rest was an option. But, again, I would try to avoid ending mid-encounter.