Should authors or readers fill the gaps in mathematical arguments?

Starting Point:We want to pass on understanding of some material. All people involved should have to spend as little time as possible overall.Everyone can be a reader at one time and an author at another.Nowadays in many mathematical texts, it is common for readers to fill some gaps.Dinstiction between gap sizes:By "small" I mean: roughly one line of intermediate steps is missing.By "large" I mean: more than that is missing.Small Gaps:Small gaps are, I think, okay. Most readers can easily fill them in mentally. This makes the text shorter and easier to navigate.Large Gaps:I would argue, however, that large gaps increase the total time effort:Qualitative argument1.: Repeated reading effort for one person:Even if you are an expert, you are still a human being who forgets. If you filled a gap once, but years later want to look something up, it may happen that you have to fill the gap again - almost as if it were the first time.2.: Many readers, few authorsA mathematical text can be written once by a few authors, but read by many people, now and in the future.Quantitative argumentAssumptions:Consider one argument whose written-out version would take about half a page.Two cases:Case 1: The argument is not written out.Case 2: The argument is written out.one author;writing effort in Case 1: 5 minutes;writing effort in Case 2: 60 minutes;n readers;each reader reads the argument twice over their lifetime;in Case 1, each reading costs 40 minutes;in Case 2, each reading costs 20 minutes;General formulasThe total time costs are:Case 1: T_1 = 5 min + 2n* 40 minandCase 2: T_2 = 60 min + 2n * 20 min.Case 1 takes more time than case 2 exactly when T_1 > T_2.That is equivalent toT_1 - T_2 > 0.The larger this difference, the more time Case 2 saves relative to Case 1.The difference isT_1 - T_2= (5 - 60) min + 2n(40 - 20) min= (-55 + 40n) min.For n=2 readers this would already be positive meaning that additional writing effort would save time overall.The larger n is, the more time is s