Actually @PJRZ. The list you are referencing states "at least 1 hour of walking, fighting, casting spells, or similar adventuring activity". They way you have phrased it suggests that each activity is subject to the 1 hour precursor. Where in actuality, only the walking is subject to the 1 hour. Reading this, the commas are important. It should be read as a list. 1 Hour of walking. ANY fighting. ANY Casting Spells. ANY Similar Adventuring Activity. A 2 minute fight is 20 rounds of combat. That is a lot of combat. There is zero chance that only after 600 rounds of combat is your long rest interrupted. The way you read this line is very important.
So to summarize:
A long rest is a period of extended downtime, at least 8 hours long,
during which a character sleeps or performs light activity: reading,
talking, eating, or standing watch for no more than 2 hours. If the
rest is interrupted by a period of strenuous activity — at least 1
hour of walking, fighting, casting spells, or similar adventuring
activity — the character must begin the rest again to benefit from it.
Anything that fits into Reading, Talking, Eating, or Standing Watch, can be considered light activity. 1 hour of walking. Casting of any spells (1 action or otherwise), Fighting (ANY Fighting), or similar adventuring activities are considered strenuous activity and not applicable to light activity.
There is also this in consideration of Light Activity...
Does the Trance trait allow an elf to finish a long rest in 4 hours?
The intent is no. The Trance trait does let an elf meditate for 4
hours and then feel the way a human does after sleeping for 8 hours,
but that isn’t intended to shorten an elf’s long rest. A long rest is
a period of relaxation that is at least 8 hours long. It can contain
sleep, reading, talking, eating, and other restful activity. Standing
watch is even possible during it, but for no more than 2 hours;
maintaining heightened vigilance any longer than that isn’t restful.
In short, a long rest and sleep aren’t the same thing; you can sleep
when you’re not taking a long rest, and you can take a long rest and
Here’s what this all means for an elf. An elf can spend 4 hours in a
trance during a long rest and then has 4 additional hours of light
activity. While an elf’s companions are snoozing, the elf can be awake
and engaged in a variety of activities, including carving a lovely
trinket, composing a sonnet, reading a tome of ancient lore,
attempting to remember something experienced centuries before, and
keeping an eye out for danger. The Trance trait is, ultimately, meant
to highlight the otherworldly character of elves, not to give them an
edge in the game.
This further expands our light activities to include; carving, Song/Poem Writing, reading a tome of ancient lore, and
I am sure there is more that can be considered light activity too.