Do L1B extension impact Approved H1B petition

[kamalmaheshwari1]

Currently I am in US on L1B which is expiring this September. 

I do have a H1B petition which was approved in 2015 and valid till Sept 2018 with same employer. I have never stamped the H1B in passport. 

Now If I apply for L1B extension will it affect my H1B in any way. I am trying to avoid stamping at this time as my wife is working on L2 EAD. 

Although I have I140, so my wife can get H4 EAD, but need to time the conversion of L2 EAD to H4 EAD as it might take up to 90 days. 

Please suggest if it is safe to take L1 extension or I should go for H1 stamp.