For How Long is the Cherem D’Rabbeinu Gershom in Effect?
I had read that CRG became effective somewhere about 1000 CE and continue through 1240 CE or thereabouts, notwithstanding the fact that it did not contain an explicit “sunset provision. Some have argued that Rav Gershon meant for it to remain in effect in perpetuity (or at least through the time a beis din of corresponding stature is in place to revoke it (aka z’man moishicach). Others dispute this view using variations of a ba’al tosif argument but instead it has been perpetuated by rabbonim over the generations, or at least until we discovered we have a shidduch crisis .