H-4 EAD application while H-1B is being ported within less than 6 months of I-140 approval

[2017h1btransfer]

I am currently working on an H-1B visa and my I-140 was approved 2.5 months back. My wife's H-4 EAD application is being filed soon. How long does it take for the H-4 application to be approved and the EAD to arrive? I have also received an offer from another company and am thinking of accepting it. Does changing jobs within less than 6 months of I-140 approval have any issues? Also, will it impact the decision and timeline of my wife's H-4 and EAD approval? Thank you!