I Bought 2 Stanley Thermoses—Neither Keeps Heat After 2 Years

My daughter and I purchased two Stanley brand thermoses through Amazon, trusting the brand's reputation and the promise of a lifetime warranty. After about two years of use, both thermoses stopped retaining heat—they no longer function as advertised. I submitted one for warranty service, and although I did receive a replacement after two months, it too fails to keep drinks hot. Clearly, there’s a recurring product defect that Stanley needs to take responsibility for.

Now I’m trying to fill out the product defect form again for both thermoses, but I can’t find the original receipts. Despite the fact that we registered the products at the time of purchase and paid a premium based on the lifetime guarantee, I am getting no response from Stanley’s customer service. Emails go unanswered, and no one is available to talk. I’m left with two defective thermoses and no support.

Is this what a “lifetime warranty” really means? Am I just supposed to throw them away and absorb the loss? I demand that Stanley honor their commitment and assist me in resolving this—with or without the receipt, especially since registration was completed. This lack of accountability is unacceptable.