Can confirm this (>14h) for T460 with the large battery option and under normal 'working load'

13 hours with the extra goiter-battery? Doing what?

Let me rephrase, if for no other reason than to give you the ability to retreat to some other anatomical metaphor:

This box, with a i7-6600U, routinely idles with the screen on at 5.5-6W with a current kernel (spending almost all of that in PC7 per powertop). Your ideas about Linux power management are just plain misinformed.

I have an X1 (Yoga).

Tiny almost weightless (feels lighter than current-gen Macbook Air) laptop, and it runs between 10 to 11 hours on the battery when doing normal work (programming, mail, web, spreadsheets etc..) on wifi with pleasant screen brightness ...

Linux power management is fine today on modern hardware... (Powertop reports 5.2-5.5 watts)

Is there anything you need to do / configure, as I am not getting that sort of battery out of my X1 Carbon running Mint. (I realize I usually leave bluetooth on, and the screen at mid to high brightness and have about 20-30 tabs open in firefox but I would still be lucky to get 5 hours out of it.)

On my machine mentioned upthread, I have a third party SSD installed which apparently fools the firmware into disabling SATA link power management. Powertop will tell you about most goofs like that.

Beyond that, run a current kernel (my measurements are on Fedora's 4.8.12 kernel). Also recognize that recent Intel SoCs have gotten a lot better at idle power draw. The "X1 Carbon" brand started with (I think) Ivy Bridge boards which obviously aren't going to perform like this.

Current/modern kernel (I run Arch), disable unneeded radios (bluetooth and lte for me), slightly lower (but still nice) brigtness on the screen and agressive tuning by powertop..