H1 Extesion Approval not received

[Boomerang]

Hi Members,
My employer filed for H1 extension in May. Though on-line verification of USCIS web site shows that approval notice has been sent on 28th June, we have not received the approval notice so far. My employer has applied for a duplicate notice.
Can any one have an idea how much time it may take to get the duplicate approval notice.

[Eve]

Approval notice

Based on my past experiences, it usually takes about 3 months to receive the approval notice.