HC that’s actually canon, just never brought back up again: Krory fainting / being very weak and wobbly on his legs after activating his Innocence is not only due to the strain it puts on his body - it’s also because of the blood loss he suffers from turning his own blood into a weapon to fight Akuma. The mix of both that strain and the blood loss is the main reason he can not keep his Innocence activated for too long time spans in battle. While Akuma bloodoil does mix with his own blood, it’s very quickly assimilated by the Innocence so long as he’s not grievously injured.
Actually a HC that’s supported by canon, but never confirmed nor disproved: In fight-or-flight situations, Krory can extend his activation time by drinking more Akuma bloodoil at set intervals of time ( every ten minutes or so ). If he’s injured, these intervals drastically shorten, and prompt him to drink more blood to keep fighting, which puts him at risk of poisoning himself with the Akuma virus. Without injuries, stress, nor using his blood as a weapon, Krory can keep his Innocence activated for increased periods of time, up to hours.