Reviving the thread.
The time can vary after Correspondence letter.
For my visitor visa, I got correspondence and passport request mail(email from donotreploy mentioning a new message in your portal account etc) within a 1 minute gap.
This time it id Pandemic, travel restrictions and it is a work-permit. So I already got the correspondence email, but no further response. 1 week passed.
Also, Correspondence letter is no assurance of an approval. My friend got correspondence letter and a refusal afterwards.
So, guys. only final decision is the final decision, not the correspondence letter.