Paris Metro/Buses

What will you be doing in zones 3-5? The only things that most visitors travel to in those zones are the airports and Paris Disneyland. You can get to the St. Denis Basilica or La Defense on the Metro without paying extra (going on the RER is indeed zone 3 and will cost more).

I agree that if the Monday to Sunday restriction of a Pass Navigo works with your dates, it's probably worth it even for a trip of 4 nights/5 days (I too am a heavy transit user in cities, and have certainly gotten my money's worth from a Navigo with fewer than 7 days!).

There's also a Paris Visite card, which gives transit for zones 1-3 or 1-5 and some small discounts for a few attractions. A 3 zone card is €37.25 for 5 days, and a 5 zone card is €63.90. It can be used for any 5 consecutive days. If you're really traveling a lot, it may work better for you than carnets of regular Metro tickets. Details on this PDF: http://www.ratp.fr/en/upload/docs/application/pdf/2014-04/partenaire_pv_2014.pdf

We've always had good experiences just buying a carnet and then getting another ten if needed. You can get them at just about any tabac shop.

Thank you for your quick replies. I appreciate the suggestions.
We have used carnets in the past, then discovered the Navigo card. (Keeping up with it was much easier for us than individual tickets.)
I will look into the Paris Visite card.

If your 4 days fall within the week, and you will be going to zone 5 or using the RER to or from the airport then just charge up your ND. There is no pass that comes close to it in price even for fewer days. Otherwise, take a cab to the hotel and get a carnet for travel around town. Get point to point tickets if you journey outside Paris. Since all Paris is zone 1 and the basic t+ tickets cover the metro regardless of where it goes, that should do it.

While you are checking the Paris Visite which I think is plenty overpriced, have a look at the Mobilis.

I think given your requirements the Navigo will still work out best - unless the dratted weekend gets in the way.....

A very good comparison is given by Paris by Train at http://parisbytrain.com/paris-metro/

Right, as Janet says, there's no better shorter-term pass than the Navigo weekly. Either just charge your Navigo for the convenience of use even though you won't use it for a full week, or buy a carnet plus whatever individual tickets you need to/from airport, Versailles, etc.

The Paris Visite pass is generally considered poor value.

Nigel's suggestion of the Mobilis is handy if you know what you're doing and are planning on running around for example the same day as you come in from or go out to the airport. Be sure to read the info.

EDIT in light of Janet's second post: correction, as she pointed out, the Mobilis specifically excludes going to/from airport. So disregard my prior sentence!!

The mobilis pass does not access either airport so it is useless on arrival day. There are some circumstances when a mobilis works but not that many. The Visite is just never a good idea (maybe if you had a room in zone 5 and were commuting in and out of the city for 4 days over a weekend. That is about it.

The Mobilis card is good for one day's worth of travel - from start of service until midnight - on Metro and buses. In addition, you don't have to worry about "backtracking", transfers or going over the 90-minute limit for regular t-tickets.
Just remember to sign and date the card and validate it every time you board the Metro or bus.

It's a good choice if you will only be in Paris for a few days. Here's the information on tarifs for the various zones:
http://www.ratp.fr/en/ratp/c_21148/mobilis/

After reading all of these suggestions, and I thank each of you for your time, I think the NavigoD is probably still the most cost effective for what we will need. We will ride the RER from CDG on arrival (Sunday) and charge our ND card for use Monday-Thursday.
We have yet to determine our mode of transport from Paris into Germany, but the ND card (zones 1-5) will cover travel BACK to CDG...or the the correct Nord in which to train from.
Thank you for all of your suggestions/expertise.

Good idea. I always figure that at 3 fulls days, I'm probably breaking even on the pass or close to it and the convenience of just being able to hop on a bus for a couple stops is worth it. And then you don't have to figure out if you're going to have any leftovers if you buy a carnet.

A mobilis is a worse deal for 3 or more days as it costs the same as an ND (or more if it is over 3 days) and yet only covers zones 1-2 and not the airport or any other of the outer zones. It might make sense for one day e.g. the 5 zone Mobilis makes sense if going to Disney for the day and a 2 zone pass might make sense if doing a lot of moving around on a day i.e. more than 5 trips. Otherwise it just doesn't make sense.