As I know, tires last 4yr from the manufactured date.
Unless u are really the super sales person of Singapore, that is the time to change. The number of km should not be use to judge if it is time to change as diff tires have diff tread wear. In sgp, our use should not wear down the tread that it requires change. Usually it is the end of life that makes it necessary.
Pvt cars to me are ok, look at the taxis instead, they are the crazy guys. driving so close on a botak tire!
eg. if you are on slick or directional tires, that is where it will tend to wear out faster or u are the super salesman. Check your tread lines.
[google it to check out how to read the tires]
Hope above helps.