A decent insulated lunch bag lasts 2 to 3 years

A decent insulated lunch bag lasts two to three years of daily use, but the moment the lining tears, the zipper sticks, or it starts holding smells, replace it.

Cheap ones can die in six months. The zipper is usually the first casualty, then the inner lining starts peeling. Once that barrier is broken, the insulation underneath gets wet and packs down — and the bag stops doing its actual job: keeping cold food cold and hot food hot.

Mold is a harder line. If you see mold inside, don’t bother trying to deep-clean it. The fabric and foam are porous, so the spores are in there. Toss it. Same goes for a musty smell that survives a wash. And don’t machine-wash a lunch bag — the agitation and heat break down the insulation and kill it early. Hand wash with mild soap, air dry thoroughly with the lid open.

Bottom line: if your sandwich is warm at noon when it left the fridge at 7 a.m., the bag is done, no matter how new it looks.

When in doubt, your nose knows.