I do know that the associations involved with the three trails (AT, CDT, PCT) plus ALDHA, give out completion certificates for those who do the whole trail, regardless of how or in what time frame. You could spend 5 years on each of the three trails and then get your Triple Crown award from ALDHA-West. After all, most people cannot take 5-6 months away from whatever they normally do when not hiking (usually working for a living), and the general feeling is that they shouldn't be penalized because of this.

Detours in effect for the specific year (mostly due to fires) are OK as they are part of the official trail at the time. In my area, nobody condemns thru-hikers for taking the spectacular Eagle Creek alternate from Wahtum Lake to Cascade Locks instead of the relatively boring PCT. Nearly everyone roadwalks from the north side of the Bridge of the Gods to Carson and up Forest Road 30 to the PCT to avoid the extremely arduous climb of Table Mountain preceded by many ugly wall-to-wall clearcuts and followed by losing most of the elevation gained going up Table Mt. Of course those on the PCT and CDT don't generally bother with White Blaze, which is almost entirely an AT forum and whch does have a number of "purists" posting. The CDT folks are resisting the idea of a "standard" trail because the many alternate routes are equally interesting and, to them, valid.

There have been plenty of incidents of thru-hikers leaving the trail for a week or even a month due to illness or injury or a family death or wedding, and coming back to complete the trail.

I personally have never had the thru-hiker mentality. I prefer to go slow, frequently stopping to admire the view and smell the flowers. While I do admire their accomplishments, I personally think that thru-hikers miss a lot. YMMV and HYOH, of course!