You won't lose residency by filing tax returns in VA. Do a search here and you will find the answer, which in short is, you can't have two homesteads.
Florida Administrative Code 12D-7.007(7) :
A married woman and her husband may establish separate permanent residences without showing "impelling reasons" or "just ground" for doing so. If it is determined by the property appraiser that separate permanent residences and separate "family units" have been established by the husband and wife, and they are otherwise qualified, each may be granted homestead exemption from ad valorem taxation under Article VII, Section 6, 1968 State Constitution. The fact that both residences may be owned by both husband and wife as tenants by the entireties will not defeat the grant of homestead ad valorem tax exemption to the permanent residence of each.