There are few fabrics as forgiving as denim. Most denim fabrics will last for years with proper care and laundering. As with most woven fabrics, denim will not fray if is sliced lengthwise, but will shred if cut along the width. In order to avoid fraying, try to minimize cross-wise trauma and wear in key areas such as the knees or hem.
To make jeans and other denim items last longer, launder in cold water with a nonbleach detergent. If desired, use a specialty detergent for dark clothing to preserve the dark dye of the fabric. Avoid tumble drying, since the friction and heat work to wear the surface of the cloth down; this leads to fading, shrinkage, softening and dye loss. Instead, hang denim fabrics up to dry in indirect sunlight.