My tea had expired(?) for about 9 years already, can I sill use it?
So long as the tea hasn't been contaminated with anything (mold growth, insects, etc.), it should be safe to use.

Depending on how well sealed it was, some of the volatile flavor components may have escaped into the air.  Tea will last in an airtight tin, glass jar, or hard metal container for many years (even a decade) past the date on the package with little loss of quality.

Cardboard packages have an advantage that they can help to regulate humidity (reducing the risk of mold), but they're not so great at keeping in the flavors on their own.  Individually wrapped teabags, especially if it's a glossy paper can offer additional protection.

My suggestion would be to look for signs of infestation -- if it's bagged, look in the bottom of the box for anything other than just tea leaf dust.  So long as there's no problems there, brew up a bag.  

If it's weak, just brew it longer, or double up the tea bags.  If it doesn't taste good, then get rid of them.