The problem is that we sweat in the shoe and condensation also forms due to the warm/cold situation. If the shoe is not dried, this is not only unpleasant, but can also lead to extremely cold feet in very cold temperatures. It is also important to note that it is not just the inner shoe that is affected, but also the shell, as moisture also collects there. I take the shoe completely apart every three to four days of use to dry it.
There are now quite a few drying options, but in the past I can only remember the mollies, which were moderately effective. This is because they only warmed the shoe, but there was virtually no air circulation. There is now a much wider range available, including combinations of dryer and blower, which promises the greatest success. I always had the feeling that heating rods only warmed up the shoe and gave the biotope an even better basis for growth. With this system, my shoes did not dry out completely overnight. The additional fan circulates the air and transports the moisture outside. The success is great and the odor remains low. With regard to the odor, there is now also an extended version with UV light, which is supposed to kill the bacteria and keep the "foot odor" even lower. I don't have any personal experience with this, but I am already satisfied with the result without UV light.