There are a lot of private sessions that go on during some conferences, but at really big meetings it is more rare. When a company wants to hold such a session in or near the conference venue, it is increasingly common that it happens before the main presentations start (i.e. 6:00 AM) or after the exhibits close for the day (after 6:00 or 7:00 PM). The conference organizers do everything they can to keep the calendar clear of conflicts during the main part of the conference and when the exhibitors are hawking their wares. This is only appropriate since the exhibitors cover a lot of the conference costs and they want lots of warm bodies in their exhibit booth.
The really early or late in the day sessions are sparsely attended as you might expect, and the ones that do have decent attendance are the result of the sponsoring company reaching out a week or two in advance to make sure the conference participants know about the extra session. That is good since most of those who bother to attend are truly interested in the content, but bad because the chance of a random walk-in is severely diminished.
As for freebies given out at meetings, this is a dying practice. Many doctors, and especially academics, won't accept anything of more than nominal value. It is unseemly for a drug company to be jacking up pricing every year when it is still giving away nice toys at the conventions. Cheap pens and Post-it notes are still pretty common, everything else is frowned upon.