EXTREME DIFFICULT LEVELS! Which Is good or Bad Extreme difficult level?

[MASTER-88]

I am really interested try completed and also make EXTREME Levels myself, but only few times i am create real Extreme levels myself i think my best Extreme levels are Levels Oh yeah More Lemmings Step 5 Levels 9, 15, 16, 18 & 19. Contains 4 main elements
1: Genius plan
2: Sharp timings
3: Very hard figured out
4: Backroute free (Have to say i miss levels 9, 15 & 18 because those backroute cannot perfect patched, but those not was bad one.. I got really succesfully 16 & 19. 19 Decimation is my Lemmings gem. Plan this level take me several years and i failed it over and over.

When played Crane pack. I´ll say Chaos levels 13 Cliffside Hostel Chaos level 26 Are you Kidding me & Chaos level 28 Denial are real EXTREME Levels. All those levels required sharp timings, super genius plan and yeah those are pretty backroute free. Though i did solved Denial & Cliffside Hostel my own ways. But heck those levels take me long. Just weeks, months and hours. Im not still never figured out that Are you Kidding me myself. Only level i´ll just give up when attempt it 7 months.

I am liked play Nota_Steve pack. Any those levels not are close even Extreme difficult, but some those are super cunning ones and its sometimes ashamed me when im not figured out that simple thing and overlook everythings else. Nota_Steve pack is awesome, but its not EXTREME. Its maybe ranked Hard. Still few hardest levels are take me 6 hours. Potholing, pendulums and No Justice. All those levels will ranked difficult hard, but sure not very hard or Extreme

How long solved Extreme level might take? Usually months and maybe you will give up.

Which is good Extreme level which keep you trying and interesting? Even you cannot solved it, but you will still keep attempts and enjoy it?

My personal turn off are very long levels where is very limited skills. Short levels keep me always trying, no matter how hard it is executed.