Mechanical Lien必须在服务后几个月到一年内加，过期就不能加了。

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.