This is actually a very interesting question, and one that I tend to think about quite a bit as a PhD student. Obviously there's no hard and fast rule, or even trends, with the varying factors that affects a particular historian's methodology or analysis. However, just one example that gets at what youre talking about. The preeminent Korean history scholar Bruce Cumings, in his first book, spends about 1000 pages over two volumes investigating 1945-1950 in Korea. But his most popular books of recent years have generally been comprehensive histories of 300 pages, looking at Korea and US-Korean history over the 20th century. Why is that? Perhaps because 1) more people read shorter but more comprehensive books, 2) he is already sitting on a mountain of evidence, so new publications don't need to necessarily show off his archival skill, and 3) he's gotten more interested in seeing if the theories that emerged from his original, narrow time period of expertise are applicable or useful in understanding a more general period. In other words, he has already established himself and his analytical personality, now he has the liberty to go much further with it.

But I don't think age is the factor here. Perspective and intentions are, which may or may not change with age. 4 years can be incredibly short or fantastically long depending on what argument you're trying to prove.

It is why I personally appreciate the scholars who try to recreate what historical events meant for the people who lived them. For example, Masuda Hajimu looks at a few months in 1950 and argues that many people in the US thought that WW3 was going to happen when the Korean War started. This point is important to his broader argument. But it's a point that often gets missed by historians who, because they're writing long after the war's end, have paid less attention to what everyday life was like. However, Masuda can't really make an argument about all of Korean history or Cold War history. He can make a very incisive point that may not be broadly applicable beyond that historical moment.

So perspectives and one's broader argument are important. To historians of war, a few months is enough time for a war to be fought, lost, and settled. But if you're an economic historian, it is barely enough time for a single company to get a loan or a patent approved. With regard to you and your pants in your drawer, a political historian might be interested in how your political views changed dramatically over that period of time. A historian of science and technology might be interested in how you bought a smartphone for the first time and started using social media. So 4 years of your pants sitting in your drawer could indeed be significant, depending on your perspective. (A historian who looks at material culture, e.g. clothes, might not be so fascinated, however.)

So it all depends on one's approach, and there's no one good way. There is a benefit to the historian who takes the long view and tries to tie it all together, but there's tremendous value in those who slow down time and show just how complex things were, and what that complexity tells us about the moment.

But regardless of the approach, it is always valuable to remember what a historical event meant for those who were living it. It helps moderate one's judgment and perspective, and can inflect even a long-view history with more flavor that has explanatory power. Someone writing about the 2000-2020 period in the future will be able to show trends about this time that we might not able to see, but that historian will likely be well served to slow down time and explain what 2001 or 2020, felt like to those who lived it, and why it felt significant for those at the time.