It's a tough call.

From the whole working illegally and affecting AOS later perspective, I honestly don't think it matters if you have already been guilty of working illegally pre-DACA. From what I understand, that doesn't bar you from being able to AOS through a family petition such as marriage. And if we are all so lucky to see immigration reform passed sometime soon, I'm sure they will be conscientious of that fact that many of us have had to work illegally and will not use that as a restriction measure. And I highly doubt you will run the risk of getting deported if you work past your expiration date, as some other poster earlier was claiming. That takes a lot of resources and government agencies don't exactly employ them if not absolutely necessary — right USCIS?

Now, from the perspective regarding your employer, it's a much trickier situation. If you work past your expiration and they realize that when you go submit your new EAD, that might cast an unfavorable light upon you. You could play dumb and act like you didn't realize there was a lapse in your permit. If your conscience won't let you sleep about keeping EAD secrets from your employer, you can roll the dice and let them know it's going to expire and see what they decide to do.

Ultimately, I think it just depends on your need. Can you go an extended period without income? How grave of an effect will losing your job have? Of course losing a job has a negative effect on all of us, but not equally. Some have dependents, some have mortgages and extensive bills, for others the job market is not good, etc. If the security of maintaining your job surpasses the importance of being honest with your employer, then the choice would be to continue working.