How long did it take you? (Impossible Boy achievement)

[soap]

So I decided to play SMB again and I told myself "Hey what if I got all the no deaths achievements ?". So that's what I've started to do (I haven't really started the Dark World yet, but calm down and don't shout "WHY DO U WNT IMPOSSIBLE BOY IF U NO FINISH HOSPITAL DARK WORLD YOU RE A POO" because I ain't a poo and I'll do so later).

The real problem is that someone said after 50 hours, he still hadn't got the achievement. And that kinda freak me out.

How long did it take you to get this achievement, hardcore gamers ?