The following is purely an openion. This is not a suggestion nor
an advise.
While there are no laid down rules about leaving an employer
who has sponsored the GC for you, there seem to be some
general norms like,
Establishing your intent to work for the sponsoring employer.
Now the question is how long do you have to work to establish this? People say a period of 6 months is good enough.
But again it depends on how the parting is handled.
It is more safe if the decision to terminate comes from the side of
the employer, rather than the employee.
There is a possibility this can raise up during the process of
citizenship/ Naturalization.
Raju