FWIW: I'm on my second Dell Precision Mobile since, oh, a long time. I bought the first in 2005, IIRC, a top-end 6500. In 2012 I upgraded RAM and put in SSDs. Then in 2014 I purchased a 6800, with 32Gb, 2 1Tb SSD, i7-4940 @ 3.10 Ghz, and an NVidia K4100M (along with the Intel on MB). I'm driving 2 27" 4k monitors. I sold the 4800 to a buddy, it is still going strong.
I do always get the 4 year total coverage. I've found that if I combine the laptop with enough server / SAN Gear upgrades for a data center, Dell drops the price significantly. The 6800 had a list price of something like $7,000.00 with everything - and my rep got it to me for $3,000.00.
Battery life running multiple sessions of RDC, Word, Excel, Chrome is good: I get about 3 hours. Huge improvement compared to the 6500, where I got 45 minutes.
I never had any issues with the 6500 that I didn't cause. I managed to pour a 32 oz glass of water into the keyboard one day. Dell came out, replaced everything, and I was up and running in a day.
There were plenty of times during beta testing that it ran for 3 days straight. I really do like the machines; I do a lot of the Adobe suite, and they handle all that just fine, as well as whatever version of Visual Studio, along with SQL Server, mySQL, etc.
I might be wrong on the years, don't call me on that.