Okay so I will be looking at the Harry Potter timeline since I believe that is our best bet of seeing what the Kotlc movie timeline will be like.
I did bring this up in the last part but I wanted to go into depth.
So as I previously stated Warner Bros had acquired the rights in October 1998 or 1999 (I've seen both being state) and the first movie came out in November of 2001. So it took almost 3 years which makes sense since they had to cast the movies, find the set, film, write the script, edit the movie, design the costume, etc...
Here is the exact timeline for filming:
The rights were bought in October 1998-1999 by Warner Bros
In late August of 2000 the official cast of the main 3 was announced
#1: November 16, 2001
#2: July 11, 2002
#3: June 4, 2004
#4: November 18, 2005
#5: July 11, 2007
#6: July 15, 2009
#7: November 19, 2001
#8: July 15, 2011
So for 8 books it took around 10 years.
Something important to remember is the fact that Kotlc is the fact that the first book alone is 2× the amount of the first Harry Potter book. So writing the script will probably take longer, meaning that the film might also be longer.
Another thing to keep in mind is that the actors for Harry Potter were on set for 12 hours a day while now it's most likely that the main actors could only do a maximum of 9½ hours.
The first Harry Potter movie was 2½ hours long, so it's a possibility that the Kotlc movie might have to be 2 parts or at least 3 hours which is crazy to think about.
The best age range for whoever is casted for Sophie (I'm just using her as a reference since she's the m/c and most of those elves are around her age) is probably 12-15 so if they were to adapt just the first movie this actor will probably be about 14-18 when it comes out which is just kinda shocking.
Okay that's my overview for now.

✌️ -Evangeline