I have castled so fast i went back in time...
How fast should I castle?
Castle whenever you wants. Early is the safest, like in move 4-8. In a tournament otb in April I castled in move 25 and my opponent resigned in move 27. In that game my opponent never was allowed to castle, and her king was dragged out in the open. If she had castled before move 9, she would have been safe, and the game would have been even. I could not castle before move 25, because I had to punish her non stop, and not let the pressure inflate. She had white, and is much stronger than me, 1590 vs 1437 Fide, so I had to play hard.
I think that too improve in chess it is smart to excersize playing in all styles. Wild, mad, safe, attack, strangle, careful......
Magnus is capable of playing in all styles. All style capasity gives more opportunities, more tools in the toolbox.
How fast should I castle?
Castling is for Whimps!
Check this out baby!

My Fortress is impenetrable!
War music:
https://www.youtube.com/watch?v=ZIbOKGTB1Po
I try to castle by move 2.