Wheel building is a repetitive process. You have to alternately work on spoke tension equality, stress relieving, centering (dish), lateral truing and radial truing. Any of these steps can affect the other steps. Usually wheel building works by making major adjustments to all of these, doing a separate round of smaller adjustments to all of these, then doing even smaller adjustments, etc.
However, there's one location where you can do a mistake. If you put too high tension on the spokes, it may be possible you can't laterally true the rim. It is possible that with too high spoke tension, a lateral correction somewhere can create an even larger error elsewhere. It is also possible that if you have too high spoke tensions, you may be able to true the rim but then after stress relieving it becomes untrue again.
Also if you have a low quality or damaged rim, it is possible you cannot achieve trueness and spoke tension equality at the same time. Then you have to compromise on some qualities. If you are compromising too much, then you may need to throw away the rim and replace it with a new better rim. This won't happen with new reasonable quality (and thus somewhat expensive) rims. It only happens with old damaged rim, or the very cheapest of rims.
I usually find that by about 4 hours, the wheel is good enough. It may be possible to fine tune it by spending 4 hours more (8 hours total) to build the wheel, but that usually doesn't pay off. You won't become magically any faster by having 0.1mm error in lateral trueness when compared to someone else who has 0.25mm error in lateral trueness -- unless you have misadjusted your brakes for no clearance.