Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Has a short life span

I loved this thermos. I used it mostly for pasta and meat. It kept the food warm all the way until lunch. After about a year of use, I noticed that the outside of the thermos felt warm to the touch (when the hot food was inside). It had never happened before - while the inside was warm, the outside stayed cool. But now, the outside is warm as well - and by lunch time the food is cold. We didn't drop or damage the thermos in any way, but the heat is escaping somehow. What a pity, it was such a great product. When I posted my original review, I gave it 5 stars, but now I have to change it to 2 stars. Works great, but not for long.