In Witcher 2 people call Geralt "old man" in multiple occasions and even Geralt himself says "I'm getting too old for this!". Anyone know how old he is? Maybe it says in the books?

I've heard 80-ish from some people, and as old as 100 from others. Separating actual numbers from hyperbole is kind of difficult, but I think it's fair to say that he's pretty damn old.

He's at least in his 60s, and could be in his 80s based on events in the books. Kaer Morhen was destroyed some sixty or seventy years before the books and there weren't any new witchers since. Those who remained alive (including Geralt) were out of the castle at the time of attack, which means that he already was a full-fledged witcher at the time.

Ahh because it never really mentioned his age in the first Witcher... unless I missed some dialog or a book. I guess his mutations also grant him longer life - which is good!

5 years after the Great War with Nilfgard... which means Geralt is 99-100 years old.
According to the books, he was 94 at the end of the last book (the massacre in Rivia).

Damn! I thought Geralt was 60, maybe 70, but nearly 100! XD. How long do the common folk live in this world? Do regular people have the same life span we do, or longer? >.<

Nope, he is a witcher, hence his life spam is longer than usual. He is also immune to diseases and ages very slowly. The same is with mages, who can live even for hundreds of years.

So here is another related questions, how old is Vesemir?

The world is Poland and the Baltic states, ca. 1271, with only a thin disguise laid over it, so we can base statements about life span on the real world. This is near the end of the Medieval Warm Period, during which northern Europe enjoyed consistent growing seasons and food supply. The best statistics there are (considering the lives of commoners were not well recorded) indicate that an adult male could expect to live to 52 on average.

Geralt, however, being a mutant, unaffected by disease, and in excellent condition, could expect to live many years longer and would well be able to carry his strenuous and dangerous trade well into his 70s or 80s at least. Vesemir is many years older than Geralt and probably well over 100.

Yes, as some people mentioned here, Geralt is ~100 years old according to the books. Toxic diet, constant exercising and regular sex with sorceresses do magic. :D I think a natural death of witchers must be related to liver failures. lol

Wait, all of this is supposed to happening on earth in Poland? I thought it was a mythical world, not a mythic setting taking place on earth. So do some the places in the book/game actually exist or have existed in real life? How about the names of the different kingdoms? Was there really a Nilfgaard and a war with them in real life?

No, the world is not Poland. I have no idea why the previous user either lied or misunderstood the plot. The world of Witcher is entirely created by Sapkowski. We can assume some of the countries are more or less similar to the real ones, but the point is that this is a completely different universe.

No, it's not happening on Earth but you can find that most of the places and kingdoms were modeled (some just by name usage) to resemble some real life nations and cities. I.e. Nilfgaard kind of resembles Dutch and Germans, Redania clearly resembles Poland, there are cities in the witcher's world that clearly resembles real European cities.

There are also geopolitical and geoclimatic events that parallel the time and place. The central geopolitical event of the novels, the Nilfgaardian Wars, is directly parallel to the Northern Crusades, though unlike the novels, the real-world event did not end with a decisive victory by the northerners. In TW1, the central faction is directly parallel to the Teutonic Knights, and the central motif, Ithlinne's Prophecy, quite accurately came true in the decades following, with the Great Famines of the early 14th C. and the Little Ice Age.

Good point, I agree with that.