Originally Posted by
aa4ever
For 9 days, it would probably be easier to buy a zone 1-2 Navigo for one week (around 21EUR each, if I remember correctly + a one-time 5EUR for the card itself) and then a carnet for the extra two days. That would cost you about the same but gives increased convenience. Might even be a few EUR cheaper.
One big advantage of the carnet is that they never expire, so any left over can be used next time.
We're just back from a couple of days in Paris and we used carnets my parents probably bought in the 1980s. They worked perfectly. Ironically, carnets left over from last year, did not work. However, we were able to exchange them for working ones at the Info booth.