This is the nth times I read about not to leave cedar shoe trees in all the time. It has some merits. Yes, the absorption is continuous. But it's not like the trees will suck all moisture out of the leather. It all depends on where you live and time of the year. Northeastern & Midwestern winters have very low humidity, especially with the indoor heat. so I think it's a good idea not to leave them in all the time. I left them in a pair of Allen Edmonds for about a month one winter, and I noticed the upper and the soles were noticeably drier and stiffer. I restored them by conditioning them and put them in a steamy bathroom for about an hour. If you live in the South, I guess it's not big deal to leave them in all the time. The most crucial moment is when you take off your shoes, you must insert the trees immediately. After all the excess mositure is gone and shape retained, you can take out the shoe trees.