Is it safe to frequently transfer hamsters into a different environment?

I've heard that changes of environment for hamsters are unhealthy and can contribute to stress related diseases, such as Wet-Tail. Every Saturday my boyfriend transfers his hamster into a plastic carrying cage (about 6x8 inches, equipped with bedding and a cardboard tube) and brings him along with him in the car as he goes places. (He brings food and water with him as well.) Is this healthy for the hamster?