Aging of whiskey increases 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity.
-- Aoshima H, Tsunoue H, Koda H, Kiso Y., J Agric Food Chem. 2004 Aug 11;52(16):5240-4.

The changes that occurred in the whiskey during aging may be the reason aged whiskies are so highly valued.