All of my Bags and Purses are made by me, I guarantee the structure of my work for up to 6 months. This means that I stand behind structural quality of my work. The seams, the attachment of zippers, the attachment of hardware, the stitches. After this I assume the items have seen much wear and tear and as much as I do believe they will hold up much longer then this, a girl has limits as to how long I will do repairs for free right?
As for the fabrics and materials we understand that everything has a limit of deterioration or a life span, so I cannot guarantee that a material will last forever as everything has a breaking point as does anything and everything in the world including us people and trees. So I cannot guarantee it will definitely last forever but it will last a long time and you will get your moneys worth. :)