Plan debate preparation time for each side.
Competitive debate requires preparing both sides of every motion, so the argument count doubles immediately. Each argument needs research, evidence and a clear line, and rebuttal preparation adds roughly another forty percent on top because anticipating and pre-empting the opposition is separate work from building your own case. Multiplying out gives a figure that explains why serious debate preparation is measured in days.
Argument count
Arguments to build = motions x arguments per side x 2 sides
Total preparation
Total hours = arguments x minutes per argument x (1 + rebuttal share) / 60
Because most formats assign sides at or shortly before the round. Preparing only one halves your usable preparation and leaves you improvising the case you are actually given.
For a familiar topic area, two to four hours covering both sides is workable. Unfamiliar or technical motions can absorb far more, largely in reading rather than in argument construction.