A reliable forecast of value development is not possible; writing instruments are no safe investment, comparable to shares. Right after purchase, the value usually falls, because private persons cannot pass on a manufacturer's warranty; increases in value are realistic only with very rare models or over long periods. Among collectors there are two main positions: keep sealed unopened as a possible return factor, or deliberately use and enjoy the writing instrument; filling lowers, from the view of purist collectors, the potential resale value. Recommended is a purchase primarily out of personal joy, not as an investment, although occasional jackpots like the Proust are also documented.