When does Arcane Echo's timer start?

I searched and there have been a lot of questions about this spell but nobody ever asked about the specifics of the timer.

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Arcane Echo (availability)
Description: If you cast a spell in the next 10-26 seconds, Arcane Echo is replaced with that spell for 20 seconds. Arcane Echo ends prematurely if you use a non-spell skill.
Energy Cost: 15
Activation Time: 2 Seconds.
Recharge Time: 30 Seconds.
Linked Attribute: Illusion Magic. Increases duration.
Skill Type: Enchantment Spell.
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My question is does the 30 second recharge timer start as soon as you finish casting Arcane Echo?

To make the example more specific I'll give an example with the 4 different points I could see the timer starting at (A,B,C,D). Let's say I cast Arcane Echo (A) and then in a couple seconds Healing Seeds (B) and then 15 seconds later cast the Echo version of Healing Seeds (C) and then a few seconds later the echo copy expires and it reverts back to Arcane Echo (D). My question is does the recharge timer start at A or B or C or D?

Thanks in advance for replies.

not sure but I dont think arcane Echo would work with healing seed

Arcane Echo only works on spells Healing seed is an enchantment

It will work, enchantments and hexes are just types of spells. In fact I believe their full description is "enchantment spell" or "hex spell".