Have a 12-hour layover in CDG coming up (arrive 11am from the U.S., depart 11pm to South Africa), and am planning on exploring the city. Bags will be checked straight through, I will have no carry-ons, and my boarding passes will already be in hand. How far in advance of the second flight would you recommend getting back to the airport, especially at this late hour? I was thinking 2 hours should be more than enough to get through security and to my gate.

2 hours is certainly more than enough - I'd argue 90 minutes would be more than enough. The other advantage is that, assuming you take the RER (and, this being France, assuming it's not on strike), then you don't have to worry about unreliable traffic.

Thanks for sharing! I will indeed be taking the RER, and have been to Paris twice before for a week or so each time, so I can at least somewhat navigate the city. I was only worried 2 hours might not be enough because I read some very old posts on TripAdvisor (understandably a less savvy group than the users here), and some people were swearing by 3-4 hours, even for transfers to Schengen flights.

Moving to the France forum for further discussion. JY1024, TravelBuzz co-moderator

TripAdvisor posters typically recommend positioning oneself at CDG 3 hours before transatlantic departures and 2 hours before other flights. The 3 hour transatlantic suggestion actually comes from reading the fine print on various air carrier's websites and I have found it a necessary on more than once occasion.

Two hours should be fine in your situation. Security lines can sometimes be very lengthy and you probably do not want to miss your connecting flight.

I would also allow one hour from Paris to reach the airport. It will probably take less but there can be many unknowns delaying your arrival.

The 3 and 4 hour time frames to which you might be referring are the times to allow between a scheduled CDG arrival and a TGV departure (3 hours) or a TGV departure from a Paris train station (4 hours).