Learning addon development

I won’t pretend I’ve done anything with WoW addons before, but looking at the API docs, wouldn’t the second return value to GetSpellCooldown be better?

duration 
    Number - Cooldown duration in seconds, 0 if spell is ready to be cast.

So something like

local start, duration = GetSpellCooldown("Flying Serpent Kick", 
    "BOOKTYPE_SPELL");
if duration == 0 then