I'm doing my master images usually at 32K these days for clean versions up to 8K and ok 16K versions. But it really depends on the location. Some are so dense in parts that even 32K will not give an aliasing free 4K version.
Concerning the speed differences at different places on the way down it is expected. In between fork points one can usually skip a lot more safely than at fork points, when embedded Julia sets are popping up or period dominance changes. The amount of corruption removal needed also slows things down considerably at times.
With the type of formations I am used to exploring, I will zoom into a feature that I like, say an "X" formation, a spiral, what have you, then I will zoom to a point sideways to the feature. At approximately 50% deeper zoom depth and twice deeper iteration depth, a new, higher complexity feature appears, then rinse and repeat. I get a nice line of similar objects in a row, then zoom off somewhere to further perturb and manipulate the shapes, making snakes out of strait lines, or "X of Xs" etc... As I zoom through the glut of shapes on my way to the next fork point, it regurgitates previous patterns in the series as well as new formations of higher symmetry.
Eventually some several thousands of zoom levels deep, and hundreds of thousands to a few million iteration depth, I have generated a formation with up to 32768 or 65536 unique spiral arms or some other fragment of shape that collectively make up the larger shapes or formations, all at the exact same iteration depth, many of which are so small they do not fully resolve in the image, all contorted into some tightly knit formation. Typically I can tell when such a formation is approaching as the iteration bands become very dense, like close circles instead of sparsely placed shapes.
Suppose at a given very deep zoom depth, the first orbit takes 30 seconds to process, then part of the image renders, then the second orbit takes an additional 30 seconds, more pixels are rendered, and so on. Typically after a few such guesses, the full image resolves. Yet the individual pixels calculated at relatively low precision generally render almost instantaneously on screen when displaying simple features, but groupings of low precision pixels take much longer to render when the highly complex target formation appears.
Again I have no issue with the render times, because it is light-years faster than the old Fractal Extreme methods of rendering every pixel at full precision. I am just curious as to why the actual (low to medium precision) fast generated pixels (not the high precision slow orbits) take longer the more complex the formation. Do these high-complexity formations require higher precision to calculate the values of the pixels? If so how does the software know whether to render them fastly or slowly?
To me, this is the biggest speed boost of Mandel Machine over Kalles Fraktaller. Mandel Machine only renderings the low precision pixels slowly when it hits these complex objects. Kalles Fraktaller seems to render more slowly all the time. That tells me Mandel Machine is doing some heavy optimization during the times I am zooming through towards the centroid and rendering relatively simple shapes.
I also noticed that "glitch" formations I seem to encounter much less frequently in the most recent build of Mandel Machine than past experience dictates. But an option to automatically zoom into the centroid or minibrot locator would be most appreciated so I don't have to click the scroll wheel thousands of times over long hours.