The longevity of fingertip and envelope moisteners depends on several factors, including the type of product, frequency of use, and storage conditions. 
Fingertip moisteners, often used to improve grip for handling paper or counting money, typically come in gel or wax forms. A gel-based fingertip moistener can last several months to a year with regular use, as only a small amount is needed each time. Wax-based moisteners may last longer, potentially up to a year or more, as they are more solid and require less frequent application.
Envelope moisteners, used to seal envelopes without licking, are usually available in sponge-tipped bottles or pen-like applicators. A sponge-tipped bottle can last several months, depending on the size of the bottle and the frequency of use. If used daily in a high-volume mailing environment, it might need replacement every few months. Pen-like applicators, which are smaller, may last a few weeks to a couple of months with regular use.
Storage conditions also play a crucial role in the lifespan of these products. Keeping them sealed when not in use and storing them in a cool, dry place can prevent them from drying out or becoming contaminated, thereby extending their usability.
In summary, fingertip and envelope moisteners can last from a few months to over a year, depending on the type, usage frequency, and storage conditions. Regular users may need to replace them more frequently, while occasional users might find them lasting significantly longer.