The Nissan Silver Bullet I have has a plug and does not leak at all.
Those push button tops always botherd me because you are relying on indirect mechanics to make the seal.
With the solid plugs on both my Stanley and Nissan thermos, if they ever leak, it's because I didn't screw the stopper on very tight, not that I have to apply that much pressure. If for some reason I got a cut in the rubber seal, it would be very easy to replace but, those push top jobs would probably require a new stopper.
You guys are right about the boiling water trick in your thermos. The problem I find when I do that with boiling water is that I find my drink too hot for the drive into work. Maybe I'm just clumsy but, I still don't like burning my mouth and tongue every time I hit a rough spot in the road or someone does an unsignaled collision manuever causing me to make abrupt advoidance manuevers.
Merry Christmas all and Drive Safe,
Sid