Activating loot reroll before the boss dies.. Does it work?

[shadowreality5]

I was told by an experienced player that there is a minimum of 5 minutes or so that a loot reroll has to be activated before it can influence boss drops. Is this true?

[FluffNStuff]

Nope

[Ihityoudie]

nope

[Swede]

Correct, that is not true. You can change to the Leprechaun Pendant right before he dies.