I got a Surface Pro 3 in February 2015 and today it is still my main personal computer. Thanks to Microsoft Windows 10's commitment and performance improvements I was able to get by until today.
The device IS getting old however. The fan is spinning constantly and the battery life is just enough to shut it down when the power would drop. Surprisingly the 8GB Ram and 256GB SDRAM are still sufficient.
Most of the slow experience I get is regarding CPU.
If I get new hardware it'll probably won't be a laptop anymore as I only sit at a desk to work on it.