Always select preservation grade materials like acid free mats and ultra violet filtering glass. Especially if a print or jersey has an autograph; this will ensure that the signature does not fade.
Mount the jersey or artifact using reversible techniques: that means never use tape or glue. In the case of a jersey, simply sew it down with a needle and thread.
Never allow the glazing (glass or acrylic) to rest on the jersey or photograph. Always use a spacer: in case there is a change in temperature and condensation forms on the inside of the glass, the extra air space will keep this moisture from wicking into the cloth or damaging the photograph.
Why go through all this trouble? We never really know what will be priceless 50 years from now. Using preservation practices will keep your jersey or artifact in “mint condition,” thus preventing any decline in its appearance and value.