Hey,

Well I actually spent a lot of time learning the fretboard (I still do actually).
Well, I say a lot of time but its actually not that much compared to the rest of my life that I will play music and "know" the fretboard.
What I like to do the most is improvising. Learning the fretboard by heart makes it so much easier to navigate and sound more melodic, less "scaly".

When I started to learn the fretboard I would name out loud all the notes on one string as part of my warm up routine. The next day the next string and so on. Then when I was starting to get the hang of that I would do all the strings everyday. Then I got comfortable with that and started to name the strings at every fret, maybe 4 or 5 frets per day (ex: fret 1 low E string = F, fret 1 A string = A# ...).
When you practice your scales, name the notes out loud too ! This will make you memorise everything faster (the notes in the scales and the notes on the fretboard).

Recently I have been improvising with notes instead of scales.
What I mean by that is that I try to avoid as much as possible scale patterns. So if I'm improvising in C major or A minor, I know thats there's no flats and sharps. So I play around on my fingerboard avoiding all sharps and flats and when I make a "long note" I try to hit chord tones (the root, major 3rd, the 5th ...) of the chord being played "under". This is helping me a lot in every way imaginable.

Take your time and make you sure you name your notes out loud ! I think thats the main reason why I was able to learn them "quickly" (took me a month to know them well and I have been working at it ever since just to be able to do it without thinking) . It will only take you 5 min of your day for a couple of weeks and you will never forget them after.

Oh and so you think I'm human and not a computer, my 40ish seconds scores are legit but not my 30ish ones. Those 30sec scores happened with a bug in the app when it started. ;) I cannot seem to get under 40sec now. Maybe soon :P