Liens can only added from "judgment debt", a debt owed by the property owner determined by a court judgment. So two parties had to sue each other in court first.
Mechanics Lien is different in that they don't need court judgments. A licensed contractor can add a mechanics lien to a property if there is a dispute about payment, without going through a court case. This helps small business contractors to at least stop the property being sold.
However, contractor cannot abuse mechanics lien process. Most states requires a mechanics lien be filed within 3 to 6 months after a service is provided. Additionally, the contractor had to sue within 6-12 months in order to turn the mechanics lien to a normal lien. Exact timeline depends on your local state law.
In your case, because GC1's last service was 2 years ago, GC1 cannot add any new mechanics lien now. If there is no existing mechanics lien on this property, I would not worry about GC1.
