Ok there are two types of valve stems,, Rubber like they normally use on car tires and metal (Brass or steel) like they use on truck tires and some flashy hot-rod type cars.
Rubber stems can go bad and leave you feeling a tad flat.. I have seen it happen several times
Metal stems can as well but.. Well .. Usually this indicates a defect in manufacture, damage or a bad washer. The washer can be easily replaced without replacing the entire item. (It can also indicate a loose nut.. Yes, in addition to loose screws many RVers have a few loose nuts.. Like the screws they are the kind you tighten with the proper tool, a wrench in this case)
But with metal stems.. If they were well made. they should outlast you.