volvo s40 timing belt milage vs years
 

I just got a 09 S40 with 39k milage on it. I took it to a shop to take a look and they told me to change tires, also consider the timing belt as it's 10 years old although not that many milage. I talked to the guy who sold me the car as I have 90 days warrantee. He said he had taken a look at the belt and there was no "crack" so he was not going to do anything about it. had my 850 for 15 years and never remember did the belt. But the shop says that I would not get a warning and once the belt breaks the car is finished. I searched online and somewhere it says 7 years or 70 milage whichever comes first, and other place says it does not need it until very high milage. And a friend says that I would get some kind of warning (by driving experience) if the belt starts to be not good. The shop also told me to send the car to them every 3700 m for oil change and 7500 m for service, so they perhaps could check if there is any crack later.
Could someone please comment if I should do it? I might have to do both tires and belt as the guy sold me the car told me that I have warrantee but he did not consider these as things needed.
thanks,

The belt is due at 120k miles or 10 years, whichever occurs first. You will not get a warning. If it snaps, it will cost you a lot more than just doing the belt on time.

and note that the timing belt service also recommends replacement of the tensioner and idler pulley which can often be the root cause of a failed timing belt.