Is that the code or just good practice? I thought a continuous load was something that was intended to run for 4 hours or more per day? Is it 4 hours non stop or just 4 hours total?
Continuous load is a load where the maximum current is expected to continue for 3 hours or more.
A fixed electric space heater is considered a continuous load, by Code. See 424.3(B).
Yes, if you are supplying electric heat, or other continuous loads. If the load is non-continuous you can go up to 4800 watts.