Translation to English: I have never tried a vapor barrier liner, and much of the reason for that is that the trips I go on typically last up to a week. However, even on shorter trips, one can notice that the sleeping bag becomes damp and partially moist. The use of a vapor barrier liner is recommended for trips from 20 degrees below zero and colder to prevent heated air from the body from condensing inside the bag. On longer trips where you have little opportunity to dry the bag, a vapor barrier can be advantageous.
Do you have any experiences with the use of vapor barrier liners? Feel free to share :)