I have gotten drastically different ECT results in pits less than 20ft apart on the same aspect. Does that make sense?
Of course snow is going to be a completely different animal on a Southwest facing slope compared to a Northeast facing slope. It'll be different snow at 6k ft versus 10k ft for sure. Observational data as you are skinning, hiking, is huge. Recent avalanche activity, shooting cracks, whumpfing, feeling layers with your ski poles, getting off the skin track onto small wind pillows, seeing if you can get a reaction, that type of stuff. When I start talking "spatial variability" I am usually talking about the slope, aspect, that I am considering. That immediate area. Ideally, you could dig a couple of pits, check out the snow, for the full range of the slope you are planning on hitting. The reality is, unless you are hiking up said slope, you can't. So you have to pay attention to all the other clues. Like the recent activity, snow fall, winds, temperature, in addition to you snow pit tests on a given slope. Terrain management when you are riding down is key too. If you are riding a wide open 35 degree slope and there is a lone tree in the middle, do you want to ride close to that tree? Probably not. Picking safe zones, riding ridges where stuff if it breaks will break below you, everything you do when you're riding, you want to keep safety in front of your mind.