It is said in several of the books that a Warder has increased strength and skill, resistance to hunger and thirst, and increased lifespan, but it never says how much longer. Obviously not as old as an AES Sedai, but longer than a man that can't channel. Does anybody know how much longer Warders live?
No longer than a normal man.
Robert Jordan answered this in an interview (item 6 on the linked page):
Do Warders have a regular lifespan?
ROBERT JORDAN: Yes they do. They hang on to what you would call 'vitality' longer than the average man, but they live a normal lifespan. They do get things out of the bond, but not a longer life.