Question on spell durations and held actions

[Syrinth]

So recently I had an encounter where the party sorcerer used Glitterdust on the enemy. His initiative was at the top of the list.

Later on, he held his action and dropped to the end of the list. Normally, Glitterdust would end at the beginning of his turn. In this instance, I ruled that Glitterdust would end at his original initiative count.

Opinions?

[Addi]

I've got no RAW answer for you, but the requested opinion.

Glitterdust would end at his original initiative count
That's right, I guess. The duration of a spell is measured in rounds so you keep track of the rounds that passed since the casting. The initiative count of the caster shouldn't be of any interest here. It's often used to keep track of those effects though.