With even moderate care, a properly-made kilt should last longer than it’s first owner. It is a surprisingly forgiving garment which can accommodate more alterations than any other item of clothing.
As with everything else, age will take its toll on your kilt. The lining will eventually need replacing. A strap may break. The stitching which holds the pleats together may come adrift.
Bring me your kilt if it no longer fits you or if it needs repair.