Abbeau,

10 years.

The chips last for many years.

The RATP is going to start experimenting with the total elimination of paper tickets next year anyway. (They use RATP employees to test things.) I presume they will be using Navigo passes loaded with certain values that will de deducted at each passage like in a number of other cities around the world. Once the bugs are worked out, I would imagine that paper tickets will disappear by 2010 or 2011.