[Kankuro]

The temperuture of the coffee will drop quickly, so I wonder if it would not resist to water consistently heaten for 2 hours or if it will fall apart after 2 hours if it contained hot water (that would be bad if you forgot your coffee on your desk).

[Steve44]

The current PE lined cups will also leak after some time. They are designed for immediate use, not as liquid storage containers. Most of them, especially the higher quality ones, will usually last a day or two before significantly leaking but not always. Don't leave one on your desk overnight, I've seen the messy results!