I am not a medical professional, but I would guess that the antibody level would decrease. I think you maintain some level of antibodies for quite some time. This would be a good question to pose to your doctor.
I think it would be a great benefit to post your before and after test results. I think everyone would gain from your test results. However, many people would simply accept their lack of symptoms as indicating they were free from the virus.
Please don't misunderstand this. I think it is wonderful and significant that you are symptom free. It's just that test results give a snapshot of what is going on inside the body. The challenge is to put all the snapshots together and figure out what they mean.