How long did lucid nightmare take?
For some people, it's taken under an hour. For others (like myself), it's taken three hours. But given how long it has the potential to be, it's better to err on the side of caution and assume it'll take several hours rather than assume you'll master it quickly, only to find you need to leave and start over later.
Does lucid nightmare progress reset?
No, the only thing that will reset is the maze. The maze will reset if you leave, or log out, which you will have to do during maintenance. All progress is saved, but the maze at the end will reset daily and can take between 20 minutes and 4 hours.
What time does endless halls reset?
The Endless Halls reset when you log out, but the map will be the same! However it has a daily reset too, changing the map to a new layout. This was my version of the map. Locations of runes and orbs might not be the same in your mazes!