It will show its age faster than it should because the cooling solution is usually not that good under load/lengthy sessions. Although it is possibly as good as it could get for on the go use, I definitely do notice bad thermals after 5-6 hours of desktop usage (SP6). This is obviously partly on Intel, since there's been very little improvements on their u processors, especially in terms of thermal output.

Imo, the best loadout right now is a powerful desktop + Surface Pro to double for both laptop and tablet. If the Surface Book 3 has a better cooling solution then we might be having a different conversation next year. I personally wouldn't mind if the solution is some detachable fan thingy like the ROG Phone as well. Also I would look out for Microsoft going Ryzen on the SP8.