I tried the ember mug (the open one), it was really only helpful if I had a full mug and I wasn't going to start drinking it for the first 30 minutes after pour

I tried the ember mug (the open one), it was really only helpful if I had a full mug and I wasn't going to start drinking it for the first 30 minutes after pouring. Once the beverage got low in the glass it no longer mattered and would weirdly dry out or develop a skin. The cup ended up being e-waste I never use. Double Walled Glass Mug is far better for an open cup experience, when paired with a hot water tank you basically have everything you need for a drink that will stay warm for the entire duration you are drinking it and you don't need to make it ahead of time. For travel a pre-heated double wall thermos is sufficient, I guess the fully enclosed ember thermos might work in those cases too.