If you ever had mono your IgG for EBV will remain high indefinitely.
http://www.pathology.med.umich.edu/handbook/Tables/Archive/6EBVINFO.htm
(I also remember seeing this in a research study)
I had the viral panel done by the Stanford CFS clinic and had an EBV VCA IgG of 7.17. One of the esteemed doctors there believes this can be a cause of CFS (There is 0 research to support this) and was convinced this was the reason why I was sick. They started me on valcyte and it did nothing for me (There is no research I know of that shows the effectiveness of anti-virals on EBV).
FWIW, a month later I had blood work done by Igenex and found out I had 4 lyme co-infections, and what also looks like a lyme infection based on my C4a and NK CD57 results. I've seen improvements since I started abx treatment.
Here is a link to the interpretation of the EBV VCA panels
http://www.mayomedicallaboratories.com/interpretive-guide/?alpha=E&unit_code=84421