EAD H1 ?

My I-140 NIW was approved already. I want to start using EAD after my H1- 6 year expired. If my I485 get denied for some reason (very unlikely), what is the worst result? Can I appeal on I485 and continue use the EAD? Is my approved I-140 still valid, so I can file another I485 later? Any thoughts on this, Xiaobaitu or other experts? IS there a time frame for approved I-140? or once it's approved, it will be valid for ever as long as my working field not changed?