I have done a lot of long duration backpacking on my own ( up to 40 days with two walk-out resupplies), as well as many 30+ day NOLS courses where we were resupplied by horse packers. Two weeks is really a watershed for almost everyone. Going out to town, even if one day to pick up supplies messes with the experience. I wish I could afford more resupply by commercial packers. Being "out there" also has a bit to do with seeing other people. I feel a lot more "out there" after I have gone a week without seeing another person.

I guess I would say it is gradual. If you feel "out there" now in 3 days, try going longer than any other trip you have done. You will find it is like peeling the skin of an onion (civilization) from your mind.

There is difference to me with 1) feeling aclimated to the new environment and 2) feeling REALLY at home and when past and future melt away to only the present. The first is accomplished in a few days; the latter takes at least a week or more.