Yet another day passed and I am able to compile and build the whole kernel in my N900 - full power development cycle.

Wall time - 3h 1m 21s.
eMMC space - 943MB.

I did a couple of phone calls in a middle without compilation interruption Skype was working too - anything as usual. Delayed reaction on button press was expected and I observed it but it was reasonable.

N900 was warm but not very. It took around 3/4 of battery resource.