The reality of it all in the sign world is, that there are two different kinds of signs. Indoor and Out-Door. There are big differences in each and each in their own can be broken down into sub categories to which application is the best fit.
As a rule, indoor signage can last a lot longer than outdoor. Mainly do to the fact that indoor signs don’t have the elements to contend with. Outdoor signs have to be built, designed, and produced to withstand many different types of environments. Rain, wind, snow, sleet, sun…some types of signs won’t last very long outdoors even if you do everything properly.
Indoor signs last a lot longer if the traffic and amount of contact from public are held to a minimum. If an indoor sign is constantly being bumped, hit, skimmed, etc it’s not going to last as long. Don’t get me wrong, there are preventative measures to assure longer life to those high traffic areas.
However, nothing lasts forever and your signs need should be evaluated on an “as needed” basis.