Shelf Life
I have seen problems with vinyl adhering to some wall paints, too. I remember reading once where 3M even mentioned by name a particular line of paint to avoid because it resisted vinyl adhesion.
However, vinyl does have a shelf life.
And even if very old vinyl seems to stick well at first, it may not live to its rated life expectancy after it's installed. A vinyl may even be formulated with an initial tack that is more aggressive, but the initial tack may not indicate how long the permanent adhesion will last.
Another problem with vinyl shelf life is that we don't always know how long it has sat on a rack in a supplier's warehouse before we get it. That's why some of the warranties specifically state that the warranty period starts from the date printed on the box.
What determines shelf life?
An Arlon tech sheet (April, 2014) indicates the cause is usually contamination of the adhesive by the vinyl itself, or more specifically, by the plasticizer in the PVC. Plasticizers, used mostly in PVC products like sign vinyl, are necessary additives. They make the plastic sheet softer and more flexible, conformable. Plasticizers may make up 20-25% of a sign vinyl formulation. As vinyl ages, the plasticizer "migrates" and eventually saturates the adhesive, gradually "deadening" it. Adverse storage conditions, such as a hot supplier warehouse, can accelerate plasticizer migration. Also, cheaper vinyls use cheaper plasticizers that are less stable. They transfer more easily. Other vinyls, like cast vinyls, have plasticizers that are more resistant to migration. Adhesives vary, too. Some are more resistant to plasticizer contamination than others.
Plasticizer migration is a big deal in some industries that use PVC extensively. Examples would be food storage and packaging, medical equipment (tubing, bags, etc), and the plastic sheet businesses that supply liners to landfills and water treatment plants.
Here is the Arlon tech sheet that talks about shelf life:
http://www.nepcosignsupply.com/store/pc/catalog/tips/14.pdf
Here are specs for Oracal 631, which I understand is the only Oracal film with a true temporary adhesive so that it can be removed cleanly, while other Oracals have permanent or semi-permanent adhesives. 631 is for indoor use. And note that the shelf life is based on a particular temperature and humidity level:
http://www.orafol.com/tl_files/cont...ldatasheets/americas/en/oracal/oracal-631.pdf
Brad in Kansas City