When are time and effects enough?

When are time and effects enough?

       Like how do we humans handle the looted Nazi art during WWII, for example.

Here are my questions:

1) How far back do we want to go? Obvious examples are the conquest of the America's, the European move into the area that has become Iran,  the burning of Meso-American religious and calendar records, or the more recent abandonment of the idea of "40 acres and a mule" in the USA.

2)  Even the amount of forested land where I live in east Tennessee on the Cumberland Plateau is now up for grabs....again.  Apparently some people want to maintain the present status quo which exists in the early 21st century, even though the same land has previously been subjected to the efforts of American Indian and European immigrants and mother nature, like lightening caused fires.  Mostly that means that now forested land in the early 21st century was previously cleared land by fire and immigrant and Native American efforts to grow food and graze cattle.

3) Mostly "they" now want to control land without buying it. The NRDC (National Resources Defense Council)  is a good example of such an organization. My perception is that these kinds of people want to use law to now try get their way.

So when is it "time" to go forward in whatever way you choose to lead? Said another way, sooner or later, what we have is what we have. An obvious example is a present farm about anywhere.