You misunderstand what I said. Any scuttle should be able to keep the lather warm for the duration of a shave. What I was saying is that the warmth of the lather lasts mere seconds once it's applied to the face. For me, the whole process involved in using, keeping, cleaning and storing a scuttle where space is at a premium is not worth the hassle for the feel of a couple seconds of warmth on my face when I apply the lather.
Noted!
For me the "whole process involved in using, keeping, cleaning, and storing a scuttle where space is at a premium" is well worth the minimal hassle. I'm a bowl latherer anyway, so the additional labor of the scuttle may add one to two minutes to my shave time at the most.
For me it's worth it, for you it's not. To each his own!