Can I proactively search for jobs given the uncertainty around my current job or do I have to wait to be terminated before I can start my job search?

My IT consulting employer, with whom I have been working for last 4 years, filed my I-140 and I-485 concurrently under the EB1-C category in November 2014. My green card was approved on March 12, 2015 (4 months from filing). The employer has since lost a number of client project/assignments (including my project in early March 2015 prior to approval of green card). I am still a full time paid employee of my sponsoring employer and waiting to be placed on a new project but afraid that my employment may be terminated due to decline in business prospects of the sponsoring employer. I understand that termination of the project (not employment) prior to green card approval should not have any impact on my current green card due to the EB1-C category. Can you please confirm? Would my termination by the sponsoring employer due to the declining business conditions described above shortly after receipt of green card have any impact on my current green card or future naturalization process? Is there any legal timeline before loss/change of employment with sponsoring employer after approval of green card? I fully intend to work for my sponsoring employer for the long term but would appreciate some legal advice given the employment uncertainty.