I have a Navigo card that was issued in 2008. Will I still be able to use the same card?
Nope. It's dead.
If you have leftover metro tickets, they're still good.
I've been reading that the Decouverte is good for 10 years. Of course you need to buy a new transit pass, but I believe the card with your picture on it is good for 10 years. We bought one in 2010 and are planning to use it this year again, just needing to buy the weekly pass.
Sandy, I'm not sure what Navigo card you got in 2008, but the Navigo Decouverte that we've used annually since about 2010 shows no expiration date. The 5 euro paid initially gets you identification and micro-chip cards in a plastic sleeve. To start travel, you pay to activate the chip. We like the unlimited Paris and suburban travel of the weekly (Mon-Sun), Zones 1-5 pass, using it for short hops on bus, metro, Roissy Bus, even for RER and suburban trains for day trips such as St Germain-en-Laye, Provins, and Versailles. You validate the card by holding it next to electronic sensors. No need to remove it from purse or wallet.