Time for a new laptop?

I thought it might be my imagination, but running powercfg.exe /batteryreport shows the truth – my laptop battery isn’t what it used to be.

Battery capacity history | PERIOD | FULL CHARGE CAPACITY | DESIGN CAPACITY | | — | — | — | | 2015-11-17 - 2015-11-23 | 5,656 mWh | 6,600 mWh | | 2015-11-23 - 2015-11-30 | 5,480 mWh | 6,600 mWh | | 2015-11-30 - 2015-12-07 | 5,177 mWh | 6,600 mWh | | 2015-12-07 - 2015-12-14 | 5,177 mWh | 6,600 mWh | | 2015-12-14 - 2015-12-21 | 5,177 mWh | 6,600 mWh | | 2015-12-21 - 2015-12-28 | 5,177 mWh | 6,600 mWh | | 2015-12-28 - 2016-01-04 | 5,129 mWh | 6,600 mWh | | 2016-01-04 - 2016-01-11 | 4,059 mWh | 6,600 mWh | | 2016-01-12 | 3,276 mWh | 6,600 mWh | | 2016-01-13 | 3,276 mWh | 6,600 mWh | | 2016-01-14 | 3,276 mWh | 6,600 mWh | | 2016-01-15 | 3,276 mWh | 6,600 mWh | | 2016-01-16 | 3,276 mWh | 6,600 mWh | | 2016-01-17 | 3,276 mWh | 6,600 mWh | | 2016-01-18 | 3,276 mWh | 6,600 mWh | | 2016-01-19 | 3,276 mWh | 6,600 mWh | | 2016-01-20 | 3,276 mWh | 6,600 mWh | | 2016-01-21 | 3,276 mWh | 6,600 mWh | | 2016-01-22 | 3,276 mWh | 6,600 mWh |

This is not the original battery that came with my Dell XPS 1645. I originally had two 90mWh batteries, but both of those wore out. The current replacement was the only one I could find online (from a 3rd party – unfortunately Dell weren’t selling theirs anymore). I bought the 1645 back in 2010, so it will turn 6 in April – that’s not a bad effort for a laptop that has been lugged around a fair bit.

And so my mind now turns to thinking about getting a replacement laptop…

My initial specs are:

Gen 6 i7 or Xeon CPU
Minimum 16GB RAM (Prefer 16 would not be the maximum)
Minimum 512GB SSD (Ideally PCIe interface)
Decent screen resolution
Lighter than my 1645 (3.06KG/6.6lb according to the kitchen scales)
A bit smaller than the 1645 (380x260mm)

Possible options:

A Surface Book would be nice, but I’ve read about stability issues - both firmware/software and also physically balancing it on your lap while typing (aka ‘lapability’)
HP zBook Studio (supposed to be out in December, but I can’t find it anywhere yet)
Titan X4K – haven’t heard of these before, but they look quite configurable (though aren’t any lighter)
Lenovo X1 Carbon 4 – Coming in February?
Lenovo P50 – (not smaller or lighter)

Let me know if you have any other suggestions or recommendations?