Generally speaking, the life of the thermos cup is only about three years, after which it will not keep warm.
When using, do not hit and deform, when the cap is tightened, do not violently twist it, clean with a neutral detergent after use.
The most feared thing about the thermos cup is bumping. Although it is made of metal, it is easy to buckle and deform to produce dents. The deformation will affect the vacuum of the sandwich and the insulation effect will be worse. Therefore, it is necessary to avoid impact as much as possible.