Instruct: Classify the given Amazon review into positive or negative sentiment.
Query: Disappointed

After using these Imuffs for 8 months the battery died. At first I thought it was enjoyable to be wireless so I proceeded to use them for at least 5 hours a day. Unfortunately for me I started using them months after I bought them (largely due to them being too flimsy and not being able to use them in the winter). So, the battery died after the warranty had expired. It took several emails to get the company to exchange them and it has been a waiting game ever since. When I receive my replacement set I'll use them until they die and I'll definitely be switching to another brand.