I added a dragon fire blast in honor of Game of Thrones. I've been making decals for a little while now and ones I have made months ago are still sticking to my windows. You have to use the smooth side (the side that was touching the build plate) and make sure the surface you are sticking it to is clean. Wet with water and place on the window, mirror or shower wall. Overall the lower the shore hardness of the flexible filament you use NinjaFlex = 85A, Flexy = 90A the better they stick. I've found the stiffer stickers Cheetah 95A are a little heavier and sometimes they fall off. That said I have a semiflex butterfly still sticking and you can always use a little bit of glue stick to keep them sticking.