Timing tension?

friends, timing change has not been 1000 km, recently sound started to sound like it is stretched. timing belt loosen over time or is it stretched?

I am relaxed, the setting is pulled out, I know that I have not heard anything from the person who has been stretched after the change until today.

After the fact that 3-5 thousand km passed after mine changed too, I heard the noise in the idle, but it doesn't always do. After going to and coming to a place, he is doing it while he is hot ... It is like 15 thousand. Is the whirling dangerous?

just like my teacher warms up, I do not understand, is it loose or nervous, I will inform you that I will go to the industry soon :)