Arti'stick: Are the Arti'stick colours durable over time?
Yes, the Arti'stick colours are durable over time. They form a good film sticker that may be stretched and repositioned as desired.
Arti'stick: Should the film stickers be cleaned, before repositioning them to another medium, to increase the adhesion?
It is not necessary to clean them, but you can use a damp cloth to wipe- off any debris or peeled paint.