I-140 Premium Processing and H1B extension

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Hi,
My PERM got approved on Jan 15th 2017 and my employer is going to file my I-140.
I am thinking to ask my employer to file I -140 in Premium Processing, If it is approved i can file for EAD.
But my H1B visa valid till September 2017 and need to go for extension in September.

Is it good idea to file I-140 in Premium processing or better do 140 in normal process wait until September 2017 to file extension, once extension is done i can go for EAD for my spouse.

Please advice me!!!

Thanks